You’re right, other people who have their head in the same hole as you believe the obvious simplification here. I’ve talked to them, and they’re proven remarkably ignorant of what others actually believe and want.
To directly refute the highlighted point, consider riots that happen after sports games. Those certainly are not all liberals milling about.
There are other factors that go into riots, as well: proximity of like minded people, ease of gathering for demonstrations, group think that encourages irrational behaviour. The first two of these are present in cities more then rural areas; cities populations are highly correlated with liberals. It follows logically that liberals demonstrations would turn to riot more because they primarily live in close proximity with other liberals who are angry enough to protest, and protest in the confines of that city. It then only takes a single bad actor to begin violence, who will be followed by others because of group think. This bad actor could even be a covert agent from another ideology intentionally trying to turn protests into riots.
But really the most stunning part of your piece is that you clearly have no idea what this election made liberals feel. You sure like to sit on your high horse and talk about the fictional world I was raised in where sports were discouraged. You can’t prove this point of view because it is part of a narrative you believe in. The facts about the existence and prevalence of sports in the lives of liberals is a testament to your ignorance.
Liberals are protesting because they are scared, perhaps legitimately, that their voices will be taken away. We already spoke with our votes, and the other voice was louder. Many liberals hear that other voice say “Hooray, we won, now we can shut up those liberals and minorities for good.” Trump’s campaign and rhetoric, amplified by a negligent and low quality media, gave liberals the fear they needed to protest. And he has not done anything to convince liberals he will not try to shut them up and ship them out; his words are meaningless as they are the tools of a pathological liar — this is extremely well documented.