If someone wants to give up dating due to their looks, age or genetics (that includes mental state) that’s a totally valid reason if you ask me. As long as it doesn’t translate to misogyny no one will get hurt. However a lot of people seem to be ticked off by this idea, why?
That’s the problem, people are very diverse. Look around yourself for examples of couples (in real-life, not online), and I’m sure you’ll find many examples of “ugly” people of all genders being in happy relationships. I know a guy with a facial deformation in relationship with a beautiful woman, I know a seriously fat couple. The forever single people I know mostly have severe mental or personality issues.