This is only a guess, but from the context I would assume that he means that if you see someone posting racist or other discriminatory toots(?) that you should challenge them.
So if they check server-side that I've read a "discriminatory toot" (whatever that means) and I haven't "challenged the guy" (whatever that means) or reported him I can expect to be banned?
Clearly the intent of that line is just that people should feel encouraged to report any hate speech.
I don't really understand why you've taken such an objection to the very concept of keeping hurtful comments to yourself on some specific public forums; but in any case I get the feeling that you're now just arguing for the sake of arguing.
