My question is, what's classified as "healthy"? Simply not having disease? If so, then yes, they are healthy. But if they're not "healthy" enough to walk up a flight of stairs without being winded or go walking through a store without hurting because they're putting too much strain on their body, then yes, I can discriminate. And personally, I will.
It's fine to have a little fat on you (I have a gut, which personally I am trying to work off, but I'm not calling myself fat because of it), but when more than 50% of your body weight is fat, that is NOT okay. I understand that you may have an issue (thyroid, for example) that makes you swell up like a balloon, but if you don't and you're 5'4" and eat ~6000 calories a day without exercise, then I have every right to call you a fat-ass. Don't like it? Do something about it.
EDIT - And I guess I should talk about the hospital point. If you're going to break the equipment, you shouldn't be allowed on it. Plain and simple. Just like if the weight limit on an elevator is 600 pounds, don't test it. It's going to be your fault when you get stuck because you were too lazy to walk up a flight of stairs.
EDIT 2 - And this is why I call myself the superficial gentleman >_>