The Islamic Sharia is very clear on this issue. Rasool Allah [saww] said:
Narrated AbuHurayrah:
The Prophet (peace_be_upon_him) said: The gravest sin is going to lengths in talking unjustly against a Muslim’s honour, and it is a major sin to abuse twice for abusing once.
Sunnan Abu Dawud, Book 41, Number 4859
So, abusing/cursing any Muslim unjustly is a gravest sin and punishment for this is ABUSING ONLY ONCE IN RETURN (And if someone abuses twice in return, it’s again a Major SIN).
This is all what Islamic Sharia says about abusing/cursing other Muslim (irrespective of being Sahaba or normal Muslim)
Abu Bakr also witnessed this fact.
Narrated AbuBakr:
AbuBarzah said: I was with AbuBakr. He became angry at a man and uttered hot words. I said: Do you permit me, Caliph of the Apostle of Allah (peace_be_upon_him) that I cut off his neck? These words of mine removed his anger; he stood and went in. He then sent for me and said: What did you say just now? I said: (I had said Permit me that I cut off his neck. He said: Would you do it if I ordered you? I said: Yes. He said: No, I swear by Allah, this is not allowed for any man after Muhammad (peace_be_upon_him).
Sunnan Abu Dawud, Book 38, Number 4350
There are a lot of occasions when Sahaba cursed each other in presence of Rasool Allah [saww], but he never ordered the killing of people on this account. We will show these incidents in little detail in next chapter.
Cursing is permitted (obligatory) in the cases if person is a wrongdoer, lair, killer, oppressor, concealer of truth etc. There are several verses in Quran in which Allah (swt) curses people who committed these grave sins.
Since these exceptional cases are not our topic at moment, so we end it here with this verse of Quran.
If a man kills a believer intentionally, his recompense is Hell, to abide therein (For ever): And the wrath and the curse of Allah are upon him, and a dreadful penalty is prepared for him.
Al-Qur’an 4:93, translation by Yusufali
So, a killer, either he is a simple muslim or a Sahabi, he must be cursed for this crime.
Rasool Allah [saww] was the “Infallible” Prophet of Allah (swt) and he brought us the message of Allah. There is a consensus upon it that if any Muslim curses Rasool Allah [saww], he becomes Murtad and punishment is killing.
Sapah Sahaba is a terrorist organisation of Nasibies in Pakistan and a killer of hundereds of innocent Shias in Pakistan. For a long time, they have been trying to introduce a new Law in Pakistan i.e. if any Muslim curses any Sahabi, he should be declared Murtad and must be killed.
But this new Law is in direct contradiction to Islamic Sharia and Sunnah of Rasool Allah [saww] and nothing more than elevating the status of Sahaba “Equal” to Rasool Allah [saww].
Let’s see more evidences from authentic hadith books of Ahle-Sunnah, if Rasool Allah [saww] ever killed any person for merely abusing the Sahaba.