What are the most "unfair" reasons you've rejected people?

I see nothing wrong with rejecting based off of looks. You're simply doing what humans are evolved to do when looking for a romantic partner. Assessing genes and traits. Both physically, and characteristically. There's nothing shallow about that, nor is there a need to defend doing it, even if it is unfair. Not that I endorse throwing people under the bus just because of their weight or whatever, but if you're not biologically attracted to it, then that's not on you. And of course, that said, attraction grows for people the longer you spend around them, if you find mental qualities you're attracted to, but the brain tends to categorize people based on mating preference within the first few seconds of meeting them. So, changing opinions about people later on down the road occurs too. But I think expecting people to do that shows a degree of unearned entitlement as it is disrespectful towards another person's feelings to begin with.

What you consider fair and not is directly linked to your morals. There is no such thing as an objective moral system. Stop trying to talk back to me with every fucking thing. It's annoying.