I hate fat people
Why is your reason for hating fat people?
Because whenever I go to the park, I see so many fat people sitting down doing nothing.
It's wrong to hate anyone without even knowing them, and especially so to judge people for their appearance.  Some people can't control the way their own bodies look, but that doesn't mean that they don't have the right to relax in a park just as much as you do.
I care about their health so I can't stand them.
It is not your job to be focused on the health of other people. Just because someone is overweight does not mean that they do not focus on their health. Just try your best to draw your perception based on who the person is rather than how they look.