I actually think anyone should be able to frogmarch invaders out with reasonable force.
Please provide definitions of 'frogmarch' and 'reasonable'.
He was probably pissed off because there is supposed to be security at these things and they clearly did a shit job.
Why? There were about 40 protesters there and all were dealt with without too much fuss. I expect that if Field hadn't gone all vigilante, they would have done the same with Barber within seconds.
But yes, the fact that a few of our betters had their posh dinner interrrupted is the real issue here.