"You probably won't understand"

I don't think there's a single more offensive statment to me personally than this one. In my extremely arrogant opinion, I'm a smart guy. One of my biggest strengths is learning quickly, right up next to quick comprehension. So when someone prefaces a statement with "You probably won't understand", my instinctive response (usually quickly supressed) is "So you think I'm stupid?"

For christ's sake, when you're trying to explain something to someone, telling them that they probably won't understand is like telling someone that they're an idiot, or at the very least, that you're vastly more intelligent than them. Either interpretation is likely to piss them off. And when the person your telling is someone you work with, who controls whether or not you ever get anything you want ever again, it's a bad plan.

I'm not even going to go into what it says when you're interviewing for a position that is supposed to be more than 50% customer support...

I think next time someone says this, I'm just not going to supress. We'll just let it all hang out, that should be entertaining.