“its just another discrimination used in the world, like racism.”
No, it’s not full discrimination and it shouldn’t be in the same category as racism. Firstly, a person is born with a race, whereas (except when it is in your genes, but even in those cases it can sometimes be avoidable) being fat is to do with how you live your life. Secondly, although there can be superficial discrimination, being fat does actually limit ones capabilities, which means it is a valid reason to treat differently in terms of where discrimination can happen (like employment).
Being fat (and by fat, I don’t mean chubby, I mean being unhealthily overweight) is a health issue and not only is it a sign that something isn’t right, but it also can lead to diseases and other problems. Which is why, overall, it’s not okay to be fat.