Pabst, there are some things that are simply not worth saying. You may completely and totally disagree with what the person is saying, but you know what? They're just not worth the energy.

To me this happens when I'm facing someone and I realize that no matter what I'm going to say, that person isn't going to change their mind. Then in addition, I do not have the energy, fire, or willingness to stoop to their level in order to agree with them. (Pick one of the three or more.) Sometimes my mental dismissal is "I don't have the time for this." or "I don't care about this enough to argue with you." Sometimes it is "I so completely disagree with you on this subject that I cannot look on you with any respect for having this viewpoint, and in fact arguing this viewpoint with you gives it any sort of creedence and so therefore I refuse to do so."

Keeping your mouth shut can be as much as sign of tiredness or unworthiness as anything else. I think it is a stronger person who knows when not to bother with an argument, than someone who is going to plunge into every single fight just to fight, just to show their bravado and "intelligence" and "my way is above all."

Discussing a viewpoint suggests that that viewpoint has merit. Not all do. As I said in a different thread with 8bit, I was dating a guy who turned out to be batshit. When he told me that equal rights for both sexes would lead to more male sociopathy because men had an innate desire for sex that would cause them to become killers if they didn't get laid, that was an argument I didn't even bother to have. His statement was so wrong on so many levels that in fact I wasn't sure where I would start with it.

Context helps too. If you have had multiple discussions with a person before and you can't get to a point where you either see eye-to-eye or agree to disagree, are you going to keep having arguments/discussions with them about future topics? Why? You know where they are going to go. (That helped me decide to leave that boy's assertion alone too; we had already tried to talk about a few other subjects and been unable to agree.)

Usually I get into Facebook arguments when I am so tired of a given person's blatant stupidity that I must point it out; frequently, too, I am tired of that person in my feed and want them to unfriend me. I know this question isn't about Facebook, but I think that should be a consideration of what it takes to get involved in a verbal brawl.

For the most part, other people's opinions aren't going to hurt you. Racism, sexism, etc - yes, those opinions will hurt you and you will find me stepping up for them pretty much anywhere and yes, especially here (but also in real life; I definitely accused someone of being, and I quote, "a sexist pig" at a 4th of July barbecue this year) - but there are also experiences on which I do not have any input because I recognize I don't know enough, and that's a great time to stay quiet too. Like, I'd (personally) stay out of any discussions about Israel and Palestine. I really don't know enough. That doesn't make me (or you) weak. That means you are capable of acknowledging and differentiating between times you should speak, and times you shouldn't.