The obvious solution is to simply never express an opinion on anything. Alternately, you could unilaterally decide you have the only opinion in the entire world that matters and thus regard the unwashed opinions of the masses as naught but the ill-conceived muttering that they are.
Or possibly, and this is a really crazy idea, stop giving idiots on YouTube reasons to flame you. Because YouTube is 99.9% comprised of idiots, and they like nothing better than flaming people. If you didn't think a video was very funny, what's the point of telling a festering sea of barely literate imbeciles who all disagree with you and each other that you didn't like it? Nothing good comes of that.
You don't exactly walk around poking grizzly bears with a stick, now do you? Some things just aren't good ideas.