People come in all shapes and sizes. Get over it. It is a part of being a human. The world would be boring if we all looked the same. Some people are bigger than you and some people are smaller; big deal. Some people wear a size 2 and some wear a size 20, does that mean one is worth more than the other? No, it does not. Size. Has. Nothing. To. Do. With. Someone's. Worth. It is that easy. Someone else's weight does not affect you, it does not matter.
Just because a person is bigger or smaller than you shouldn't matter, you should not think any different of them. Society has trained us to value the thin. The "Instagram famous" who edit their photos and go days without eating to maintain that sought after physique. These people are put on a pedestal and are valued over any other body type; causing boys and girls to starve, binge, purge and many other self-destructive behaviors because they do not look like the people in the photos.
Weight is not a measure of worth.
It is hard to realize this but there is no correlation between weight and what kind of person someone is. It is what is on the inside that matters, not the outside.
We need to accept people no matter what. No matter their size, gender, race, sexual orientation or anything else. People are people and all people are worth something. Being curvy does not mean you are more of a real person than anyone else. I have been told that I am not a real woman because of my weight. What does weight have to do with it? It is insulting hearing other people decide what kind of person I am based on my weight.
Saying that a thin person isn't a real person in order to make yourself feel better about your size is incredibly rude and insensitive. Just as a thin person saying that another person isn't pretty because they are bigger. Both are examples of bullying based on someone else's size and one's own insecurities.
Be happy with your size and you will find it is much easier to accept someone else's. Stop making assumptions about a person based on their size. As a society, we are too obsessed with body image and looking "perfect" but there is so much more we can be doing. Learn to be happy with yourself, and you will find you are less bitter about everyone else.