Sometimes I write any letters when I'm really pissed off with something. Then I bin them.

In the last resort there are three ways of getting someone do what you want.You convince them, you charm them, or you threaten them. Sounding off about how rotten they are doesn't fit in with any of those strategies. It might make you feel better, which is fine - as I said, write it and bin it.

Or maybe sing it, if it scans - except then, if it's a good song, you might start feeling a snaky sort of gratitude to the occasion of your wrath.