We can see cases in Sahih books or other famous books of Sonni brothers that some of Sahaba performed sins in age of prophet of Allah (s.a.) that caused them to be punished.
Do you repeat that they were all impartial? And they did not make a mistake? What a justice is this which if they perform a great sin that has lawful punishment and they will be punished due to that sin, justice will remains constant in its place?
I point to some cases for example:
A) Na’eemaan Sahabi drank wine and holy Prophet (s.a.) ordered to beat him with sandals.1
B) A man from Bani Aslam tribe performed incest and Prophet (s.a.) orders to punish him by throwing stones.1
C) In the story of Afak holy Prophet (s.a.) ordered to punish some persons.2
D) After holy Prophet (s.a.) Abdurrahman ibn Omar and Oghba ibn Hareth Badri drank wine and Amr ibn Aas governor of Egypt punished them. After that Omar evoked his son and punished him again.3
E) The story of Waleed ibn Oghba is famous that he drank wine and performed dawn prayer four Rak’ats (part of prayer) instead of two, then he evoked to Medina and punished.4
And there are other cases that are not expedient to say. Do we ignore the truths again and say they were all impartial?!
1- Sahih of Bokhari, vol. 8, page 13, Hadith No. 6775, Ketab Alhad (Book of Punishment)
2- Sahih of Bokhari, vol. 8, page 22, Hadith no. 6820.
3- Mo’jam Alkabir, vol. 23, page 128 and other books.
4- Alsunan Alkobra, vol. 8, page 312 and lots of other books.
5- Sahih of Muslim, vol. 5, page 126, Hadith no. 1707.
