People speaking the truth in really ignorant or confusing ways doesn't make it less true. It just makes that person a bad communicator. You can't negate the truth of a statement by shooting the messenger, even if they failed to get their message across properly. That's called an "ad hominem" attack, and it is a recognised logical fallacy. You can talk about the expression of the idea, but you must make an effort to understand it.
Mokalus of Borg
PS - Wikipedia actually calls it an "informal fallacy" or an irrelevancy.
PPS - Which doesn't make it any better.