Quarrel on sizeism

I'm ubersensitive to sizism, sexism and racism. Admittedly, I'm an attractive young women with Asian looks, so my personal pet peeves on the three subjects are:

Sizeism: you should totally eat that, with your figure. I don't like skinny dancers. I thought bellydancers needed to have big boobs. Yes, sizeism is for all shapes and sizes! And most of the time it's men commenting on women, isn't that swell.

Sexism: the double standard regarding female behavior: if I have sex on a third date, the guy calls me easy. If a guy has a dozen one night stands, he's just a regular good old chum. If I'm calling in sick, people ask me if it has anything to do with having my period. Noone ever asks a guy when he calls in sick if he's having trouble with his prostate.

Racism: two out of three meetings with strangers start with the question 'where are you from?'. Because knowing who I am is not as fascinating or important as knowing why I look so different from Dutch people. Some random remarks: your kind like's garlic. I bet you know how to cook Indonesian. Ah, so you're a dancer? It's easier for you, Dutch people are not that into dancing.

So I called a coworker out on making sizeism remarks and how uncomfortable I am with those remarks. I could have done that with more tact, style, technique and according to the proper feedback rules, but I didn't. Instead I got emotional and angry and I got into an argument. This post is a way for me to structure my thoughts and try to be more reasonable about it. What is it that bugs me? The reason for me to discuss the matter was when person A and person B had a conversation about girl C 

A: did you see how fat girl C became?
B: yes, such a shame really, she used to be real pretty
A: I don't understand, we know her parents, she has a nice boyfriend, if she'd only stopped eating so much and started exercising
B: I can't believe people let it get so out of hand. I mean, we're not supermodels, but we're taking care of ourselfs.  

Logically, my objections are:

1. I don't really care how fat/thin someone is. It is not their single most defining feature
2. the implication that fat people are not pretty.
3. the reasoning that the person in question has no reason whatsoever to be unhappy, so no reason to have a problem with food
4. the implication that we have absolute control over our bodies and CHOOSE to be a certain way. in reality, 90% is ghenetics, only 10% is what we do.
5. the implication that your physical appearance should have a high priority. To many people, it is not a priority and that's okay. There are so many other things that you might find important, like love, compassion, being with people you like, etc.

I won't go into detail about the onbjections as they are pretty straight forward. Let's have a look at the arguments that surfaced during the discussion:

1. Why do you care about this remark about someone else? You are not fat.
And since I'm not black, I should have no problem with racism either.

2. I don't mean it like that, she is a nice girl, I just wish she would take care of it because I know she's unhappy with her weight
And judging her with harsh words is going to help her how? Do you wish her to take care of it because it makes you feel uncomfortable to see her? Because you can't imagine a fat person to be happy?

3. Well, how can I not remark how big she is getting?
It's simple: don't. There is no reason why you should make strongly worded hurtful remarks about someone else's physique in a regular conversation with another person, ever. Just because you see it, doesn't mean you have to talk about it. And even if you do, try to do so in a respectful way. This is a person you're talking about, not an object. 

What I should have said was:' When you made a remark about how fat X has became, you used words like 'fat pig' and strong emotions. It made me feel very uncomfortable and hurt. Please use neutral words when you want to comment on someones's weight/size/shape.'