Most Helpful Guy
Not all guys are like that. Some girls Will do the same thing to you. But most likely they do it because they are jealous. they want to make you feel bad about yourself since they feel bad about themselves. they just are haters.
Most Helpful Girl
First of all: no one makes you have low self esteem. Yes, bullying can lead to it but at the end of the day you can choose to rise above it. I know when you're young it's hard but get rid of that victim mentality sooner rather than later.
Also, I've not met many guys who do this other than typical bullies or assholes, so it's useless trying to find the reason why they do things. They simply do, they suck, as such their opinions aren't worth giving value to.