And that's the right impression.
If by "bears" you mean the fit guy a bit hairy with a big beard, yeah, those are not frown upon. OFC many people love bears.
If you mean people who have trouble dealing with their weigh, yes, they are frown upon. Not only by the straight community which tends to shit on people for being overweight anyway, not particularly because they're gay, but also by the gay community which is soooo shallow, all about appearance, and seems to think the gym is like a second house for gays.
And I say this with no bitterness as I do have a few pounds to lose, but nothing too bad. On the other hand, I'm into bears. Not into "unhealthy" big, bit I'm into bigger man than I am. I'm really nothing fantastic, yet most of the time the bears I've flirted with tells me they don't understand why someone like me are into someone like them. And yes, they are vastly frowned upon, in the gay community too. My boyfriend is actually bitter towards the gay community because of it.
So yeah, maybe it's harder to be fem (because people in the street may see you're gay and give you shit for that), but body type wise, you better be a twink than a bear, no contest.
For your question, I told him I like big guy, but I want him to be healthy though. It was hard to hear and he gave me shit for saying it, but he's working his way towards it (I didn't asked him, he wanted that before he knew me). He's getting more confident, he can joke about it, he knows I love him no matter what, but as he told me today he'd love to get rid of the "spare tire" he got around the waist.
And if you think about it, he wasn't happy when the topic first came. But I don't think he would like it neither if I told him I love him BECAUSE he is overweight.
But thankfully we're past that, I learned to love him as he is, he learned to be less sensitive about it and hopefully some day he'll reach his weigh goal.