AG, when you say, in your OP "Oh dear! I would have ..." etc., I assume you are referring to the mob violence - please correct me if I am wrong.
The short answer is – yes, it would have everything to do with the counter-demonstration.
Violence from, and by either side of this melee is inexcusable and cannot be reasonably defended by anyone at all.
It is hardly reasonable to object to a group of bone-headed thugs by imitating their behaviour on the streets in exactly the same manner.
Ideally, the fascists should have stayed at home, and if not, then the anti-fascists should have stayed at home, because although each would advocate their right to express their views, the only thing that does get expressed is violence, mayhem, and stretched police resources being stretched further needlessly.
No-one emerges with any credit from days like this.