Thug's Veto
A 'Thug's Veto' is when violent and/or threatening activists and/or protest groups, usually on the left of the political spectrum, force the closure, cancellation or disruption of an event that they don't agree with by means of intimidation or threats of violence and chaos.
"Did you see how the New Zealand Prime Minister endorsed a thug's veto when she said she was 'proud' that controversial speakers were shut down by protesters in her country over the weekend?"