> Try to first believe what they said instead of getting paranoid.
If he wouldn't believe it then he wouldn't be paranoid, the whole paranoia angle only exists because of the complete vagueness of the accusation.
It's literally telling somebody "You did somebody wrong, we won't tell you what you did or to whom, but consider yourself on notice", how is anybody supposed to react to that except with complete paranoia?
> If the other people in the office start doing small talk to you, then you answer, don't engage the other way around.
Sorry for putting this frankly, but why? It's either the same rules for everybody or no rules at all. Why are other coworkers allowed to initiate private small talk while he is not?
What are you basing this difference of rulesets for different people on? On the mere existence of an anonymous accusation that doesn't even detail what exactly he did wrong? Or maybe even superficialities?
Don't you think that whole setup is quite one-sided and could just as well be considered as bullying?
> Just accept what they said and try to take this a learning a experience that your behavior does not come out as professional where you are working at the moment.
Again: How is he supposed to learn anything from this when he isn't even told what he did wrong or to whom? What part of his behavior? In what exact situations? As is, it's such a generalizing statement that it might as well just be a personal insult.
> Try to pay attention to that on your next job.
Remember that thing you did wrong and nobody ever told you about? Don't do that wrong the next time!
Much has been learned, very educational.
> That sometimes you might think you are being friendly and people see you as creepy.
And what you might think is creepy I might consider funny in a friendly odd way. There are always two parts to communication of any kind: A sender and a receiver. Getting the right context across, and preventing misunderstandings, involves effort on both ends, not just the sender.
The only thing anybody learned here is that he's considered a horrible creepy person, with exactly zero context or reasons given as to why he's supposedly such a bad person.