Personally, I conclude that “clichés are just that ... clichés.” They're vast oversimplifications, good for baiting the occasional “troll” but frankly not worth the time of day.

Funny. "They're vast oversimplifications" is exactly the failing of cliches in general, but it's also the failing of your statement :)

I think you'd have a very hard time making "all perl programmers are green-haired chinchillas" into a widely-accepted cliche. Ditto for "SQL is used for low-level programming close to the metal". The reason cliches become cliches is that they have (or at least had at the time they became widespread) some level of truth about them. The reason cliches are disparaged (if it weren't disparaged, it wouldn't be called cliche) is that the truth is generally one-sided or outdated.

The problem with cliches only comes when you accept them as the whole story, or as eternal verities. A completely false cliche, with no actual justification or germ of truth behind it, is a rather rare species.