I wouldn't necessarily support a "fat acceptance" movement, but I would support a movement that encouraged our media to stop glorifying the stick figure. This would be easier to put into action and a goal more likely to be obtained then fighting the stigma that "fat" has. More than anything I would suggest encouraging a healthy average weight, and proper eating and exercising habits instead of forcing people to accept fat people.
I honestly don't know why anyone would want to be either bone thin or obese, that's when you start to get health and mental problems, there is nothing okay with encouraging that with society acceptance. However it isn't fair that our society is obsessed with being skinny, because that is exactly what gives young girls body image issues that drive them to either overeat or have anorexia (or bulimia). I think it would be fair to encourage improvements in this area, but I don't think they should ask people to accept obesity as normalcy.
No one will ever truly accept that, you cant change truth into acceptance in order to be politically correct, just like no one really thinks that "niggas" arent god awfully annoying. funny enough society now tells me I cant even mention that fact, let alone say the word and I think that's bullshit. If that's what these people are going for, to force people not to mention how other people make them feel, then this becomes an infringement on MY freedom. I don't give a shit if people want to be overweight, I'm certainly not going to tell them what to do, but I don't think anyone will ever be able to change their minds about that sort of thing... its just not humanly possible.
I must mention however that girls who are healthy weight are MUCH MUCH more attractive, and as it was mentioned before those are usually the girls that make better girlfriends because they aren't insecure about their bodies. Call it a sign of strong mental health, with a bonus of "more cushion for the pushin". Of course I'm not talking about the Michelin Man here, just a beautifully curvy woman.