Though I don't think anyone really needs to prove themselves here since 99.9% of us here are just random pseudonymous users, I don't think he/she's wrong at all.
I think that proof of oneself is what has made some members more reputable than others here. There are some members a lot of high ranked members can vouch for here and that's because they've earned the trust of the community. So, to that extent I will say that at some point we all have that opportunity to prove something.
Again, we may be seemingly anonymous with our monikers but that isn't enough shield to hurtful words. This is bad for those who don't have the backing of the community especially when wrongly accused or misconstrued. Words (hurtful or not) transcend the mere facade of usernames. People go through a lot in life offline. We shouldn't compound it with unguarded utterances in the guise that everyone needs to grow think skin.