Personally, I think those examples are kinda shallow. When looking at the sentiment, I was thinking more like a good friend of mine. She's a lesbian feminist punk and it grates on her every once in a while when closed-minded fools say things like, "What you don't like guys?!?!" or imply that she's some sadistic, man-hating, female supremacist or something. She has to laugh, since she much prefers hanging out with us guys. How could she be a man-hater when she loves hanging out with us and tearing up the pits with us at shows?
Or I was thinking something even simpler. Like you would look at my guitar player with his mohawk, tattoos, and patched up clothing and think he's some degenerate loser when he's one of the most responsible guys I know; he graduated culinary school, holds a steady job, pays his bills on time, and is probably one of the most mature and respectful 24 year-olds you'll ever meet. He's passionate about being a punk, it's in his bones, and he hates it when people tell him that he has to "give that up" to be a responsible adult. Like I said, he's already a more responsible adult than some folks twice his age.
Or even just looking at my death metal musician friends and thinking they're scary guys who'd eat your children, but they're easily the nicest, most down-to-earth people you'll ever meet. (ASIDE: It's the cute boys who sing forlorn love songs who are the biggest jerks.) But death metal is the style of music that's in their bones. And even then, people are often surprised that they not only listen to other forms of music, but love it. Loving metal doesn't mean hating "real" music. Heck, most metal guys I know listen to a lot of Vivaldi, Panganini, Miles Davis... It also doesn't mean you're a terrible person. Heck, like I said, some of the warmest, friendliest, and most steadfastly loyal people I know are death metallers.
But, again, it's the whole idea of people wanting to put you into a neat little box of black and white. It's the "if you're not with me, you're against me" mentailty. And that's immature, because there is that grey area. Just because I'm right doesn't automatically mean you're wrong. But that's how people hear it. Just because you're for X doesn't mean you're against Y, ya know? And that's not even going into the whole rant about thinking a negative based on someone's look.