When broken right down, I'd say it's the same as taking a positive outlook on a negative situation. You've got this thing, and it's bloody hard to live with, BUT you can make it easier. You can get away with things you otherwise couldn't, and why shouldn't you when people annoy you? It's just a more ready excuse to get away with something without incurring any of the potential consequences.
Everyone wants to feel special, or feel better about themselves. These disorders are a ready-made excuse to do just that, and they don't have an "expiration date" of sorts either - you can use them, and re-use them, as many times as you like, whenever you like. The downside is that you have to live with it, and the downside is probably substantially more prominent in the majority of cases, but when you consider it in that light, why shouldn't people use these things to their advantage, to empower themselves, when it is so difficult to do so otherwise? Because it's an inconvenience to others? Yes, it is, and consideration would be nice, but consideration goes both ways. It depends on the individual, the severity of their condition, and their attitude towards it. How often do they use their condition to their advantage? Why do they do it? How do they expect to be treated?
I'd judge it on a case-by-case basis. It's difficult for me to empathise or sympathise, as I don't have these conditions - I have a few metaphorical screws loose, but nothing of the nature of what is being described; at least not at present, thankfully - but I've been on the receiving end of this treatment a few times, and the scenarios and people involved have been markedly different each time. On occasion I've gotten really annoyed, I'll admit, but for the most part I tend to ignore it, or take it in stride. It's just another social interaction, and that sort of thing is ingrained in who we are: we know how to respond, or not respond, to certain behaviours. Delving into that would take me all night, and it'd be both irrelevant and wholly unnecessary.
It's annoying when people do it, especially when it's so painfully blatant, but...well, I personally can't begrudge them that, because in their situation, whatever it is, I would probably do the same sometimes. It's a way to cope, to feel better, to feel empowered when it's very difficult to feel that way. Just another tool in the arsenal. If you think of it like that, rather than a crippling, horrific condition you'll never recover from, wouldn't that make it more manageable? In that sort of situation, who WOULDN'T look for a way to make their life more bearable? Perhaps I'm reading too much into it, but that would be how I'd see it.
I'd say this can apply to psychological disorders as well, though. But then, perhaps I've become cynical from spending too much time on Tumblr, where people advertise and compare their psychological disorders like it's a competition to see whose is objectively "worse" in some circles. But I suppose that is another way to empower oneself...albeit a strange, fairly twisted one that almost makes a mockery of the condition, whatever it may be. It really does depend on how often you do it, I think and, more importantly, what the reaction you're aiming for is.
Hopefully that didn't step on anyone's toes...
