Sexism and racism are so similar!! I'm going to use your post and substitute a few words because what you've said is like saying there are some whites out there who feel that Blacks are okay and some who do not. If you don't want to be discriminated against, you just select from the whites who are not racists . . . so what's the problem? When the overall structure is sexist or racist, there is no escape. Discrimination against heavy people not only affects them in the romantic realm, it affects them in employment, transportation, housing, and other human interactions and services across the board. And just imagine, these people pay taxes too. I'm speaking out against the overall sexist/patriarchial structure that penalizes females who are above a size 1/2. I'm not just talking romance.
People who think negatively of a woman because she's a certain weight are contributing to sexism. And no, you don't have to date or be romantically linked to someone to repsect them as a person. But if you're thinking she's a slob, she's lazy, this that and the other that's a form of prejudice and to me it's wrong. It's saying 'ewww' at a HUMAN BEING that some would protest against. There are male physiques I'm not as attracted to, particularly excessively skinny or overweight men. This doesn't mean I haven't or wouldn't (assuming I was single) cross them off if I developed an emotional attachment to them. Regardless, I don't show hatred or think negatively of a man simply because he possessed these traits.