The biggest reason is tone and the motives of the person who is disagreeing with you.<p>The worst arguers on the Internet don&#x27;t just disagree; they bring a moral judgment along with it. &quot;You&#x27;re wrong for believing in X, and the fact that you believe in X <i>makes you a bad person</i>.&quot; If you have enough people who agree with this, (and this often has absolutely nothing to do with broader support for X or whether X is actually bad or not) you actively feel hated, demeaned, etc for believing in X and voicing your opinion. Even being polite will provoke an enormous amount of vitriol simply because it&#x27;s very easy to lump in a polite X-believer in with preexisting ideas that all people who believe X are assholes.<p>A lot of people react to this with, &quot;Well, good. There are a lot of shitty Xs that people believe, and people really should be afraid to say those things out loud.&quot;<p>That&#x27;s all well and good for some opinions; I&#x27;m not advocating being polite to, say, neo-Nazis who are denying the Holocaust or advocating genocide. But people rapidly expand X to &quot;whatever I disagree with,&quot; and the result is that we treat disagreement on <i>legitimate, reasonable issues that people will naturally disagree on</i> as equivalent to endorsing genocide and believing that the Holocaust didn&#x27;t happen.<p>It doesn&#x27;t help that the Internet naturally magnifies hatred because it&#x27;s very, very easy for 5,000 people to get ahold of something and leave one really nasty comment apiece. They spend 10 seconds writing a comment, but the person who originally posted X gets 50,000 seconds of written vitriol. It&#x27;s overwhelming.<p>As a result, there are certain issues on the Internet (and in real life, for that matter) - <i>vital</i> issues, <i>important</i> issues, that I <i>will not touch</i> because they are far too likely to dump a massive amount of vitriol on me. I have better shit to do. As a result, the best possible outcome for me is not to engage entirely.<p>And then those exact same people who dump anger and hatred on all believers in X complain that said believers in X are &quot;avoiding them.&quot; Well no shit they are, who would volunteer for that?