Which mainstream Islam are you talking about??
Islam has hundreds of versions, like every other religion, and this was proved by the oldest Quran found in Yemen.
I do not believe in anyway that Quran asked you to stay away from anyone even the pagans.
I strongly believe that no religion ever forbids its followers from showing kindness to those who have not fought you.
Islam also says that "let's not be hostile to anyone except the wrongdoers".
So I wonder where did this generalisation of Pagans come about??
@Slav Defence
I might need your help here.