I think I am not going to block a friend who is being accused of abuse
Why aren't you going to block him? Abuse is pretty serious.
Because one day I might need him.
You should not block your friends. That is wrong. But if he abused others, you should probably block him and not be selfish about it.
He said he was sorry.
What else is he going to say besides "sorry"? You are too sweet and gullible, and I think he knows that and tries to use this to his advantage by manipulating you into thinking he is a good guy. I know you are smarter than this, so please think this through and do the right thing.