Protecting the dimensionally challenged

The FreeP reports on a bill proposed in Massachusetts that would ban discrimination by height or weight. "Organizations like the National Association to Advance Fat Acceptance and the National Organization of Short Statured Adults have rallied behind the bill." I'm not exactly tall myself, so I'm not defending my own type here, but I think this is taking anti-discrimination laws a little too far. There is a danger in any anti-discrimination law, that it is usually impossible to prove discrimination; that the burden (of proof and legal defense costs) is unfairly imposed on the alleged discriminator (i.e. the employer); and that it doesn't allow for rational discrimination. There's a strong case to be made for banning discrimination on the basis of race, sex, religion, or sexual orientation - the social benefits in those cases seem to outweigh the dangers of government-imposed fairness. But height and weight too? Is hair color next?
The problem, I realize, is that once the floodgates of anti-discrimination laws were opened with the Civil Rights Act, the logic of ending at any particular case is flimsy. So Barry Goldwater had a point. I just think his point was weaker regarding race and stronger regarding weight. And I may be a snob for saying this, but is legitimizing obesity good for society? Isn't there a necessary function in stigmatizing overly fat people, so that they stop eating so much? (There's a reason it's called an obesity epidemic. Some incentives in the other direction would be wise.) Short people may be a different matter, but seriously, how do you prove you didn't get a job for being too short? (The same way you prove you didn't get it for being gay, I guess...it's a problem.)