However, having an opinion on someone's opinion or appearance now that is another matter, if you have a problem with another person then that is your problem. What gives you the right to voice your mean thoughts and insult another person? You don't have that right to effect another person, especially one you haven't met before. What are you gaining by commenting on someone else's behaviour or appearance, it doesn't effect you how they look or act. You gain nothing, it's pointless. But if trying to lower someone's confidence genuinely brings you pure happiness, then I'm afraid you're in need if some some self evaluation instead of evaluating others.
A little rant kind of which was inspired my a little mean comment on another of my social media, which helped me out of my writer's block!