This may have been true at one time, but in the age of Youtube videos and live broadcasts being a popular vehicle for all of the above, I don't think folks care anymore about anonymity.

It's a toxic race for attention and engagement to either a.) generate revenue, b.) acquire some taste of "fame", or c.) both. Being anonymous plays a role in some corners of the internet, but the ones that are contributing the most to the cultures you mention above don't depend on anonymity. They're being perpetuated and propped up by very knowable online identities, and I highly doubt the folks doing the propping think they're safely anonymous.