I'm tired of this debate, both sides usually come out looking poorly. I know what I want my body to look like (based on what's possible with my genetics and metabolism). I know what body types I find sexually attractive in potential partners. I know how to eat healthy. Caring too much about what other people are eating and what they weigh is only going to put me in a bad mood, so I avoid it. I do think modern society is broken in many ways when it comes to nutrition, health, and weight; but if someone is happy and confident in the way they look, power to them. Honestly.
People can make a lot of personal remarks when you are unusually thin, and I've had plenty of negative feedback in my life. I've always been underweight for my height (naturally so, I have a very small frame - and I have a big butt for my size, and visible muscles in my upper body, so these days people don't think of me as 'skinny' even though my BMI is hitting 18 for the first time in my life, and I am 27). However I have had many overweight friends in my life, some of them carrying over 100 extra pounds, and our experiences can't and shouldn't be compared. Most people get made fun of at some point, but the level of vicious cruelty fat people often are the target of is a whole other level... just my two cents.