It's not a historical fact. At all.I didn't say physical violence 'invalidates', I said it discredits. That's not a perennial question, it's a historical and political fact.
Honestly don't see how throwing soda cans can be anything other than disturbing. I wonder how you'd all respond being on the receiving end of such an attack.
You or many do probably support the current violent protestors in Venezuela even though they are, well, violent. So the generalization is wrong.
Protest are meant to be disturbing too so I think you don't get protesting is all (edit: or you might have meant that differently, my bad!). Now if this is strategically thought out or just not helpful in this specific situation is another question. Because I think it isn't.
But the generalizations you put forth are ones that I and reality itself, reject.