What would you say if I told you that I despise fat people?
Why do you hate fat people?
I know too many of them and they need to learn to control their eating
Not liking someone for their personality is fine, but for their weight is just wrong. They are still a person and you don't know their circumstances. Talking like that is probably going to lose you a lot of friends in the future.
I can't stand people who eat too much. They will get no mercy from me.
Being prejudiced against overweight people is wrong and hurtful to them in the process. Take a look at your anger and see if you don't see some of them in yourself so that you might find a little compassion for them.