In reading some of the discussion around L Word actress Leisha Hailey being kicked off a Southwest Air flight for kissing her girlfriend, I was reminded of a favorite defense trotted out in favor of discrimination. "But I think publicly kissing your partner is wrong no matter what your sexuality!" Indeed, its Southwest's defense here, too. Its not the sexual orientation, its the behavior. There is roughly no reason to ever take this sort of line seriously.
Its a pretty common tactic and that's what we need to recognize. This is a tactic and even an earnest proponent of it references it while willfully ignoring the larger social context. They think if they, individually, are willing to apply something to everyone, that's a get out of prejudice free card. That doesn't really work on a personal level, and it is pretty much insulting on a cultural level.
I'll take the cultural level first, because, well, it's low-hanging fruit. Trotting out this kind of "well, I'd discriminate against everyone" line in response to instances of discrimination is just an attempt at derailing. It doesn't matter why you'd do it. What matters are the systems of discrimination. By centering the discussion on your hypothetical motives, you just seek to distract from focusing on the larger social issues at play. You make something about you which isn't remotely about you. The reality is, your supposed even-handedness isn't what is happening in our culture. When gay people are scolded for showing affection, there is no counterpart among straight couples. Straight couples aren't being thrown off airplanes for kissing. Thin people aren't subjected to ridicule for eating in public. Men aren't viciously denounced for being sexually assertive. Your standards aren't the point, because your standards clearly aren't what's happening.
I feel this generally fails on the personal level, too. All too often, "but, its wrong for everyone" thinking only ever comes up when its wrong for the group society agrees its wrong for. Its essentially a hallow claim. You protest that you'd feel the same way if this were happening to a socially privileged group, but you never have to worry about that because it never will happen to a socially privileged group. Its just something to make you feel better about cheering for the stigmatization of marginalized groups.
The fat community sees this played out a number of ways. I suspect the most recognizable would be the fashion policing of fat bodies. Fat people are often scolded for their clothing choices by people who insist they'd find it distasteful on any better. Not coincidentally, though, they only ever voice that disgust with fat people for whom it is culturally protected to scold and demean for their bodies. They love claiming their prejudice is without regard for body size, but they never question their own actions and how even-handed they actually are when directly scolding people. They might like to think it and maybe they'd snark at celebrities, but I've seen little reason to think these people are seeking out thin bodies to police at the rates they are seeking out fat bodies. People like claiming they think its wrong for everyone, but the next time you hear someone say that, ask them to demonstrate that thinking in action. They like saying that to scold marginalized people, but how much time are they actually out there being publicly outraged when privileged people do it? I doubt many would even pass that test, much less be able to justify the recentering aspects of that position that draw attention away from social discrimination.