Of course, I reply politely to these people that this is simply not the case, that music theory is not bollocks, that it serves a purpose, can expand your sound, and lets you really understand music. Upon this, a small flamewar usually ensues, and some heated words are exchanged from both sides.
Among the primary arguments of the people who militantly refuse to learn music theory, the most prominent one is that if they learn theory, they're going to "sound like everyone else" (you won't). A few other ones are "I can learn it better if I just teach myself." and "my shit is so experimental [read: awful] that it doesn't need music theory!" (haha). Now, I would go alot easier on these people if their music was actually worth listening to. By and large though, its absolutely terrible stuff, and its clearly evident that they had no clue what they were doing. I know this is pretty subjective territory, but still, it was plainly evident.
Anyways, it just annoys me when people are so steadfastly ignorant when it comes to trying to learn about music. Oh, and the best quote from talking to one of these people:
"Music theory is for talentless musicians!"