Please research implicit bias.

Also, please recognize that “hard to overcome” implies an effort to overcome and recognize that that thinking is wrong.

If I had to justify it, I would say that I have been conditioned over the course of 20+ years and continue to be conditioned to see non-fat people as desirable and fatness as gross. And to some degree it is rational - fat people are more likely to die young, experience health issues, struggle with hygiene or everyday activities; all things you don’t want in yourself, your partner, or people you rely on. It’s also clearly a mental health issue, which comes with its own stigmas. It takes time to overcome and unlearn all of that.

> How do you justify that to yourself?

Fat people often smell really bad, but they don't realize it. That's one way to justify hating someone you haven't met, yet.