Good insightful article and I do appreciate the careful parsing you do.
“Why are white dudes … ?” Good question. Here is an answer: Because Straight White Men don’t need permission to insult or deprecate anybody and are entitled to do so; nobody else has that privilege or sense of entitlement. SWMs can spew hatred or plain old vitriol with impunity even against other SWM and in that qualitative sense may even be non-discriminatory. However, I suspect that that is not true quantitatively: the quantity of vitriol they spew against gender/sexuality/racial/ethnic minorities is probably much greater than against someone like you who they probably view as a fellow, albeit misguided.
Why is hate speech not better regulated on-line? Because straight white men write the regulations and are rarely the target of hate speech. Regulating violent and hate-generating speech would infringe on their “freedom” to bloviate. And the upside for them (from regulating it) would be … what?