I’m sometimes sarcastic, but I’m trying to give it up altogether. It’s bad to be sarcastic because civility over disagreements is a good idea, and sarcasm is uncivil. But there’s another reason to avoid it.
There are mistaken arguments that sound vaguely persuasive when cloaked in sarcasm whose flaws would be obvious if you tried to say them straightforwardly. People say things like “oh, yeah, I’m sure if cigarettes are in plain packets then no-one will ever smoke again, that’ll solve the problem”. What’s the non-sarcastic form of this argument? The obvious turn-around is “I think that there will still be smoking if cigarettes are put in plain packets”—but put this way, it’s obvious that it’s arguing against a position that no-one is taking, since a reduction in smoking that stops short of elimination is still a good thing.
Or “the minimum wage is great, let’s have a minimum wage of $1000 an hour and we’ll all be rich”. Here the argument is at best incomplete—we can all agree that a $1000/hr minimum wage wouldn’t be a good idea, but you’re going to have to spell out what you mean this to tell us about, say, a $15/hr minimum wage. If there’s a real argument behind what you say, you should be able to make it without sarcasm, and exactly what you are trying to argue will be clearer to all of us, including yourself.
2017 addenum: One further problem is that you put the onus on the other person to reconstruct the non-sarcastic form of your argument in order to reply to it, and you reserve to yourself the opportunity to muck them about and be uncivil some more by telling them they got it wrong while still failing to set it out.
Please do try to avoid the obvious jokes in your responses, thank you :)