Bernie Sanders supported the carpet bombing of Yugoslavia. He is not a socialist.

You can be critical of politicians and I have nothing against that. But those two things, if the first thing is even real, are not even close to being even remotely connected. One is strictly foreign policy while the other is pretty much economic policy (or at the very least social policy) and definitely not foreign policy. A person can be a socialist and want to nuke every capitalist country in the world. It most definitely isn't a good idea nor one people should support, but it doesn't mean that person isn't a socialist. Similarly you can criticize Sanders for supporting bombing Yugoslavia (Once again, if it's true. I don't know and frankly I don't care), but his foreign policy does not mean he isn't a socialist.

I'm also not saying he's definitely a socialist. Some of his political positions are socialist while others are more socialist-adjacent, so he's somewhere on the border of socialism and depending on your own beliefs he may or may not be a socialist. I haven't gone over everything he stands for (because I'm not American and I don't care that much about American politics) but I personally would call him more of a social democrat than a democratic socialist.