Only women should have a say in the abortion debate simply because they are women.
Why is that so dumb? The pro-choice position is all about a woman's right to choose.
The problem is that making that argument preassumes a 'pro-choice' way of looking at the issue. For 'pro-life' types it isn't (ostensibly, obviously there's misogyny very present in the movement) uniquely about women, or about women as a group.
Pete Singer's arguments are pretty awful but they're more disgusting than dumb.
For me, I'd say that it would have to be...most common Christian apologetics, actually, would fall into this category. So is the idea (though this may only be current on certain college campuses) that a socialist government would as a matter of course legalize drugs and polygamy (deployed, of course, at people who think that such is desirable).