Of course fantasy and reality should be kept seperate, but that does not mean that fantasy is completely innocuous, especially when it's out here where anyone can see it.
I'm definitely not against "humiliation" bits like the ones described in the post directly above this one - those are pretty harmless. And yes, there's pretty much always going to be some degree of being pleased at what another considers to be misfortune, however minor, in lovers of BE. But I've seen more people than I'm comfortable with slip too far into this category.
Let's face it, a lot of the real women whose experiences we find exciting would be hurt and angry to discover this fact. I'm not saying that this alone makes something wrong, but when one actually prefers women who hate their large and/or growing breasts, it gets pretty hard to reconcile that desire with healthy, consensual relationships. Sure, it's possible for a woman who's actually ok with something to play at being upset for the sake of fantasy, but surely this will be the minority of cases.
Really, I've seen this sort of thing too often lead to guys emphatically preferring for things to happen to a woman that excite them over what's actually good for that person. I wish I could say I thought that all or even most of the people thinking this way held it exclusively in the domain of fantasy, and had an underlying respect for women and would ultimately agree that it's best they do what's best for them (which can, for example, include things like a breast reduction for mainly emotional reasons, whether we like it or not), but I really don't.