I try not to. I don't always succeed.
See, it generally doesn't actually do anything. Oh, in the rare cases in which there's a large and interested audience of Undecideds, it is possible that a well-crafted set of points and verifiable examples may sway minds and/or hearts, but in most cases the onlookers take it as one of those Sergio Aragonés cartoons in the margins of Mad magazine, or at best an episode of Spy vs. Spy.
I will ask for cites -- claiming "X" without supporting evidence is plain lazy on This Here Innerweb -- and where the law is already clear, I'll call folks on wishful thinking. But most arguments boil down to a matter of politics or taste (or both) and debate often turns on stupidly fine points. (Would there be fewer shootings if there were no guns? Yes. Would there be less violence? Doubtful at best. So which outcome did you want? -- And who "wins" depends on the answer to that last question. Either way, when the online debate is over and the principals are sitting back and sipping coffee, nothing in the real world will have changed.)
If you've got a friend who holds some opinion you think is plain wrong, ask yourself what matters more, the friendship or trying to get in there and take a wrench to the contents of their skull? Ask yourself, is this person doing harm to others on the basis of their opinion, or is it just another of the damfool notions wandering around loose in people's thoughts? Ask yourself, "When did I enlist in the Thought Police?" 'Cos you probably didn't. And you've probably got damfool notions of your own. I sure do.
I'd rather have friends than an echo chamber. Sometimes we just have to disagree and go on.
T. R. MCELROY'S STREAMLINED TELEGRAPH KEYS
8 months ago