Censorship does not require violence.
The concept of "self-censorship" is a testament to this.
Simply being afraid of some sort of consequence for sharing ideas is a way to shut down free and open discussion. Censorship does not require out-right physical violence.
Mental and emotional attacks are also powerful ways to control people, and the problem here isn't violence. It's censorship.
Censorship isn't bad because it can be caused by violence. Violence is not the "evil" here.
Censorship is inherently bad, no matter if it's caused by physical violence, or another mental or emotional threat.
What you are talking about is peer pressure and shunning. These are social norms that @dana-edwards discusses here:
https://steemit.com/politics/@dana-edwards/do-social-norms-trump-the-law-or-my-response-to-the-free-the-nipple-controversy
Well, with 'self-censorship', the only guilty party of the censorship is the individual remaining silent.
Censorship is just more effective when backed by violence, or threats of violence.
Otherwise, its just a social pressure situation, which I think Steemit has demonstrated, politically 'incorrect' things can be said openly all day and even be highly rewarded.