There are plenty of ways to distribute and obtain revenge porn. Nothing unique and especially nothing efficient about blockchain. Blockchain isn't some special higher power, from a data perspective it's not substantively different than a server with media on it.
It's not the job of the software protocol to address social/legal problems. That's the job of governments and law. If the law in particular jurisdiction prohibits certain illegal content, then the node operating in that jurisdiction will be compelled to follow it, blockchain or not.
It is objectively better because one has an option and the other doesn't.
What option do you have if twitter _does not_ filter out media that you deem bad?
Conversely, what option do you have if twitter _does_ filter out content that is not objectionable to you?