Peevishness is always a bad idea. The minute you say out loud "my pet peeve is," you're choosing to let something annoy you. And in a world full of annoyances like movie theater texters, bed bugs and Ty Pennington, that's a recipe for round-the-clock rage.
But in grammar, peevishness is especially unwise. By letting other people's speech bother us, we're not just obsessing over something beyond our control. There's a good chance that what we're obsessing over happens to be something we ourselves are wrong about.
For example, some of the people reading this probably got a nails-on-a-chalkboard sensation from my last sentence because it ended with the preposition "about." Lots of people were taught, especially in the middle of the last century, that this is a no-no. So when they catch someone else ending a sentence with a preposition they get annoyed.