"Positive portrayal of gay characters" is iffy.
I don't see what is wrong with this. Social behavior may be iffy for other reasons, but for positive portrayal of gays? I don't believe that that is a bad thing.
The movie isn't good for kids, but not because of the gays.
I watched this movie with my dad a few weeks ago, and it’s really good. The opening scene was very uncomfortable to watch, though, and I recommend skipping it. Other than that, it was a hysterical movie that had me laughing when I thought about it.
I haven't seen many mockumentarys (like "Borat" or "District 9") but I do watch "The Office" regurlarly so I know when they're making fun of something, sort of satire like "Tropic Thunder." I'm glad to say it was very funny, and I recently saw a real dog show on TV, and their impressions of the eccentric trainers were spot-on!