Below set of narrations indicate that the Imam's (as) have clearly indicated that we Shia's should not be cursing or doing Tabarrah from each other.

Hadith 1:

عنه، عن علي بن الحكم، عن محمد بن سنان، عن الصباح بن سيابة، عن أبي عبد الله (عليه السلام): قال: ما أنتم والبراءة، يبرء بعضكم من بعض، إن المؤمنين بعضهم أفضل من بعض وبعضهم أكثر صلاة من بعض وبعضهم أنفذ بصرا من بعض وهي الدرجات

It is narrated from him (Muhammad ibn Yahya), from Ali ibn al-Hakam, from Muhammad ibn Sinan, from al-Sabah ibn Siyabah from Abu Abd Allah Imam Sadiq (as);

Imam Sadiq (as) said, "What is this disavowing and disassociation of yours? Some of you disassociate from others (among yourself's). Among the believers some are better than others. And some are those who pray more than others, and some are of sharp insight than others. Such are the levels/ranks (of belief)."

[al-Kafi, Vol. 2, Pg. 45]

Hadith 2:

أبو علي الأشعري، عن محمد بن عبد الجبار، ومحمد بن يحيى، عن أحمد بن محمد بن عيسى جميعا، عن ابن فضال، عن الحسن بن الجهم، عن أبي اليقظان، عن يعقوب بن الضحاك، عن رجل من أصحابنا سراج وكان خادما لأبي عبد الله (عليه السلام)

قال: بعثني أبو عبد الله (عليه السلام) في حاجة وهو بالحيرة أنا وجماعة من مواليه قال: فانطلقنا فيها ثم رجعنا مغتمين قال: وكان فراشي في الحائر الذي كنا فيه نزولا، فجئت وأنا بحال فرميت بنفسي فبينا أنا كذلك إذا أنا بأبي عبد الله (عليه السلام) قد أقبل قال:

فقال قد أتيناك أو قال: جئناك، فاستويت جالسا وجلس على صدر فراشي فسألني عما بعثني له فأخبرته. فحمد الله ثم جرى ذكر قوم فقلت: جعلت فداك إنا نبرأ منهم، إنهم لا يقولون ما نقول. قال: فقال: يتولونا ولا يقولون ما تقولون تبرؤون منهم؟

قال: قلت: نعم قال: فهوذا عندنا ما ليس عندكم فينبغي لنا أن نبرأ منكم؟ قال: قلت: لا - جعلت فداك - قال: وهوذا عند الله ما ليس عندنا أفتراه أطرحنا؟ قال: قلت: لا والله جعلت فداك ما نفعل؟ قال: فتولوهم ولا تبرؤوا منهم، إن من المسلمين من له سهم ومنهم من له سهمان ومنهم من له ثلاثة أسهم، ومنهم من له أربعة أسهم، و منهم من له خمسة أسهم، ومنهم من له ستة أسهم، ومنهم من له سبعة أسهم، فليس ينبغي أن يحمل صاحب السهم على ما عليه صاحب السهمين ولا صاحب السهمين على ما عليه صاحب الثلاثة ولا صاحب الثلاثة على ما عليه صاحب الأربعة ولا صاحب الأربعة على ما عليه صاحب الخمسة ولا صاحب الخمسة على ما عليه صاحب الستة ولا صاحب الستة على ما عليه صاحب السبعة، وسأضرب لك مثلا إن رجلا كان له جار وكان نصرانيا فدعاه إلى الاسلام وزينه له فأجابه فأتاه سحيرا فقرع عليه الباب فقال له: من هذا؟ قال: أنا فلان قال: وما حاجتك؟ فقال: توضأ والبس ثوبيك ومر بنا إلى الصلاة قال: فتوضأ ولبس ثوبيه وخرج معه، قال: فصليا ما شاء الله ثم صليا الفجر ثم مكثا حتى أصبحا، فقام الذي كان نصرانيا يريد منزله، فقال له الرجل:

أين تذهب؟ النهار قصير والذي بينك وبين الظهر قليل؟ قال: فجلس معه إلى أن صلى الظهر، ثم قال: وما بين الظهر والعصر قليل فاحتبسه حتى صلى العصر، قال. ثم قام وأراد أن ينصرف إلى منزله فقال له: إن هذا آخر النهار وأقل من أوله فاحتبسه حتى صلى المغرب ثم أراد أن ينصرف إلى منزله فقال له: إنما بقيت صلاة واحدة قال: فمكث حتى صلى العشاء الآخرة ثم تفرقا فلما كان سحيرا غدا عليه فضرب عليه الباب فقال: من هذا؟ قال: أنا فلان، قال: وما حاجتك؟

قال: توضأ والبس ثوبيك واخرج بنا فصل، قال: اطلب لهذا الدين من هو أفرغ مني وأنا إنسان مسكين وعلي عيال، فقال أبو عبد الله (عليه السلام): أدخله في شئ أخرجه منه - أو قال: أدخله من مثل ذه وأخرجه من مثل هذا

Abu Ali al-Ash’ari has narrated from Muhammad ibn ‘Abd al-Jabbar from Muhammad ibn Yahya from Ahmad ibn Muhammad ibn ‘Isa all from ibn Faddal from al-Hassan ibn al-Jahm from abu al-Yaqzan from Ya’qub ibn al-Dahhak from a man of our people, Sarraj who was a servant of Abu Abdillah (as) has said the following: 

"Abu Abdillah, (as), once sent me with a group of his followers for an task and at that time he was in Hirah (a place near Kufa, Iraq). We left for it and returned depressed. My bed was in al-Ha’ir (a comfortable private quarter). I went there in an upset condition and threw myself thereat. At this time Abu Abdillah (as) came in saying, 'We have come to see you,' or he said, ‘We have come to you.’ I then sat up straight and he sat in the middle of my bed and asked me about the task for which he had sent me. I reported to him and he thanked Allah. 

Thereafter, a mention of certain people came up and I said, 'May I be sacrificed for you, we disassociate (do Tabarrah) from these people; they do not say what we say.' 

The Imam (as) then said, 'If they love and support us, but do not say what you say, do you (still) disassociate from them?' I then said, 'Yes, we do so.' 

"The Imam (as) said, 'It is just like this ('A'immah’s case). We have what you do not have. Should we disassociate from you?' 

I then said, 'No, may I be sacrificed for you'

The Imam (as) said, 'It is just like this (the case of Allah). With Him there is what we do not have. Do you think we should give it up?

"I then said, 'No, may I be sacrificed for You. We should not do so.'

The Imam (as) said, 'Be friends with them and do not disassociate from them. Among the Muslims there are those who have only one share, those who have two shares, three shares, four shares, five shares, six shares and those who have seven shares. It is not proper for those who have one share to blame those who have two shares, or those who have two shares to blame those who have three shares, those who have three shares to blame those who have four shares, those who have four shares to blame those who have five shares, those who have five shares to blame those who have six shares and those who have six shares to blame those who have seven shares. I will give an example: 

"A man had a Christian neighbor to whom he preached Islam attractively and the neighbor accepted. It was early next morning when he knocked at his (convert’s) door. He said, 'Who is it?' He (the preacher) said, 'I am so and so.' What do you want? the (convert) said. 'Make Wuzu, dress up in your two cloths and join us for prayer,' said the preacher. 

The new convert then made Wuzu, dressed up in his two pieces of cloth and joined him. They performed prayers a great deal. Then they prayed the morning-prayer, then waited until it was light. The convert got up to go home and the man asked him, 'Where are you going? The day is short. The time left to noontime is very little.' The new convert sat down with him until noontime and they prayed the noontime prayer. Then he said that there is very little time to afternoon prayer. He prevented the new convert from going home until they said the afternoon prayer. He then wanted to go home but he (the preacher) said, 'It is the last part of the day and is less than the beginning of it.' So he (the preacher) stopped him until they performed the prayer at sunset. Then the new convert wanted to go home, he (the preacher) said, 'Only one more prayer is left.' He then waited until they performed the late evening prayer and then they departed each other. Next early morning he (the preacher) went and knocked at the door of the new convert. He (the new convert) asked, 'Who is it?' He (the preacher) said, 'I am so and so.' He (the new convert) asked, ‘What do you want?' He (the preacher) said, 'Make Wuzu, dress up in your two pieces of cloth and join us for prayer.' He (the Christian man) said, 'Find other persons for this religion who have more free time. I am a poor person with a family to feed.'

"Abu Abdillah (as), then said, 'He (the preacher) took him (Christian) into a thing in such a way that it took him (the new convert) out of it. Or that the Imam said, "Took him in like this and forced him out like that."

[Source: al-Kafi, Vol. 2, Pg. 42]

Hadith 3:

وعن محمد بن حمدان، عن أبي عبد الله ع قال: إن كنتم تريدون أن تكونوا معنا يوم القيامة لا يلعن بعضكم بعضا، فاتقوا الله وأطيعوا فإن الله يقول: يوم ندعوا كل أناس بإمامهم

Narrated from Mohammad bin Hamadan,

Abi Abdillah Imam Sadiq (as) said, "If you want that you are along with Us on the day of Judgement, then do not curse one another among yourself and fear Allah (swt) and Obey (Him). Indeed Allah (swt) says, "On the day We will call all men with their Imams" (17:71)

[Source: al-Fusoul al-Muhimmah fi Usoul al-Aymah - Shaikh Hurr al-Aamili, Vol. 1, Pg. 358]