Can you link to a source that he was forced to leave by an armed intruder please? I have not heard about that. My understanding is that the event was opened and Milo took the stage. People were there to listen and he spoke. Outside, a socialist protester was shot by a Milo, Trump and NRA supporter who claimed on FB that he was punched and his MAGA hat was stolen an entire hour before he shot someone. And he has not been charged. Yet. I am not convinced that the shooter was even really there to listen as, like may others, he could have spent that time inside the hall instead of outside protesting and posting to FB about being assaulted and asking Milos for a new MAGA hat. I am also pretty sure there was no governmental restriction on MY's right to speak. He spoke. He chose to end it at the time of his choosing. No governmental authority prevented or forced that. If the "tough guy" instigator can not handle the consequences when he intentionally foments the foreseeable backlash (for the sole purpose of attention whoring IMO) , he has no one to blame but himself. He is a "tough guy" that likes to play the victim.
I was thinking of the UC berkly violence but I guess something similar happend in Davis https://www.google.com/amp/s/amp.cnn.com/cnn/2017/01/14/us/milo-yiannopoulos-uc-davis-speech-canceled/index.html?client=safari https://www.google.com/amp/s/amp.cnn.com/cnn/2017/02/01/us/milo-yiannopoulos-berkeley/index.html?client=safari In both cases protesters use violence to shut down speech. If we accept that as normal and acceptable without punishment of the violent individuals it sets a horrible precedent. Today it might be some alt right wignut in Berkeley but tomorrow it might be a BLM speaker, Muslim speaker or an abortion clinic in Alabama. The point is protecion of speech should be grey and only in cases of clear and immediate danger should it be allowed to be suppress.