there are a few separate issues that can be sub-categorized from "being fat".
- Health issues
- Society Issues
- Personal issues
- Rights issues
- Work Issues
Personal and societal issues are close, but probably deserve their own category. How you feel about someone being overweight is a personal issue, same as how they feel about themselves. Obviously you can be whatever size you want, eat whatever you want, and look however you want. Other folks are also perfectly okay to feel a certain way about how you look. The problem comes when folks decide "how I feel" is the same thing as "how you should be". Just because you don't like the way someone looks, that doesn't mean you can throw all the other categories I mentioned at them to force them to change into something you like better. That's just manipulative.
If you want to discuss the other categories as separate topics to how you it makes you feel, then you should. I personally want people to live long, healthy, productive lives. This is best done by everyone getting proper sleep, eating quality foods (but not more than needed), working out, continuing education, continuing growth of emotional maturity, and not being a tool. Generally if you live life to maximize happiness and minimize suffering, you tend to be more fit and not fat. But not always, and everyone's mileage varies. My attraction to someone doesn't really enter into the picture.
But in the "work" and "society" categorize, perceptions of other people influences a lot of decisions, so how folks are treated based on how they look is important. Definitely should be discussed, just not conflated with other categories, that's all.