Pretty sure that's a little rose-tinted though, jourdain. Lloyd George once gave, or tried to give, a speech on the somewhat obscure but apparently very interesting issue of Tariff reform, and the mob that arrived in protest might very well have torn him apart had they got his hands on him (that will have been about 1900).
Also Peterloo. Or the Gordon Riots. Or the General Strike of 24 and all that "bring down the government" stuff in the 1960s. Or Cable Street. Or Orgreave (although perhaps that's a bit too recent since apparently Corbyn doesn't want to shut up about it). Or Toxteth. Or the Battle of Lewisham. Or Notting Hill. Or Chapeltown. Or ... or... or...
This is not to say that I find the protests at all acceptable, and I am saddened and sickened by such people. They do nothing really to further their cause and just give opponents an excuse to ignore anything that comes out of their mouths, even if it's uttered by sensible, not-violent-mobster types. But this idea that such violence is somehow new is a fairly bizarre reading of history.