I think you bring up some fair points, and this is something I do often. I don’t hate someone for disagreeing with me. I often try to agree to disagree. But there is an assumption here in the title that some of the people you’re arguing with, won’t be stupid or have really stupid ideas.
On its own it’s not bad for people to have stupid ideas, the problem is when that idea goes from being a mere idea to an action. The problem is when an idea is so stupid and so potentially harmful, that it bears debunking. Maybe you have a real concern for this person, and even if this person is disagreeing with you, you still care about them.
Maybe that idea could get them in serious trouble. Sometimes people can be so ignorant on a subject that it’s a detriment to them, and in those situations, I think it’s perfectly reasonable to try and convince them that their position is wrong.
Having had my share of disagreements, I find that the people getting the most emotional are the ones who can’t even remember where they got the stupid idea in the first place. Sometimes we accept things as fact without really questioning it. Then we can’t remember why we starting believing something to be true because we took something on faith alone and didn’t do any research.
While there is a tendency to assume people are stupid, there is also a tendency to assume people are more intelligent than they actually are. We project intelligence onto them where it doesn’t exist, and then we assume that they must have some higher reason for believing what they believe.
There’s a tendency to assume that all opinions and ideas are equally valid, but they aren’t. Some of them are just plain bad. People get smarter and become better thinkers when challenged, but they have to want to be better critical thinkers. They have to be willing to admit when they’re wrong, and be willing to be wrong.
Perhaps it’s better to say that some folks are lazy thinkers because often that’s closer to the truth than them lacking basic intelligence. Sometimes people wrap emotions and part of their identity to an idea, so we hesitate to tell them when they’re wrong.
Now sure there are tons of situations that you can just let go. In fact, most of them you should probably let go because it’s wrapped up in things that don’t matter. But in those few times where serious things are at stake, I think it’s perfectly reasonable to tell someone that their opinion or ideas on something are stupid, when they are in fact, stupid.
There are times when you do need to take a side. Sitting on the fence and being neutral is fine when all parties are respectful reasonable individuals. But sometimes there are people who just want to watch the world burn, who don’t care about other people, or can’t be reasoned with. Logic and reason go out the window, and at that point, you have to ally with someone and pick the lesser evil to fight the greater evil.