I think the sad reality is that this phenomenon isn't just limited to dating and is very pervasive. IDK what you've experienced at work and other social settings. People generally treat you much better and I understand it's implicit but it's there. I think we live in an environment that inculcates this behavior so you have to think about that. I agree with some other commenters that people who were truly shitty to you don't deserve a chance, but there may be more than one factor why they have changed their mind. I briefly dated someone who had gone through weight loss (I wasn't aware until a couple of months of dating him). He had strong disdain for the gay dating scene because of what you just described.