I'll answer anyways, it's because onlookers view conversations made online and this shapes their thinking. When people like yourself admit to never taking your interlocutor seriously, this just serves to legitimize what the other person is saying. I am a Marxist, I believe people can change, and that I shouldn't obscure my views or fail to try to bring people up to better levels of understanding. I also have had people thank me directly, so positive reinforcement helps.