Yes it is. The protesters need a good pants down across the knee paddling with a wooden paddle. Preferably with holes in the paddle. Or a chair across the head. Or a steak knife between the ribs. Whatever it takes to get the message across.The diners are acting inappropriately. They should pick up their chairs and start teaching the protesters how to behave with a chair upside the head.
Notice that they don't start their crap in a biker bar. Just places where the audience is assumed to be docile.
So you react to non-violent protests with violence? Yeah that's totally okay.