AITA my friend has an obese 13 year old

My friend has a morbidly obese 13 year old and continues to feed the kid awful awful food. No spots or exercise either. I decided to politely say something to him about health risks with both the kids weight and what they cook and feed him. They now hate me and they've told people I fat sham kids and stick my nose in other people's lives.

It's like I'm a bad guy but you're setting your kid up for disease and giving McDonald's and pizza everyday is wild.

Was I really a bad guy here? I was never rude either. AITA