http://www.lmgtfy.com/?q=block+button
If you are so mentally weak that a few preppy girls from your high school can convince you to kill yourself on Facebook because you have an ugly feature or you're not popular, the world's better off without you. By the time you're allowed to freely roam the internet you should have built enough character as a person to not throw an emotional tantrum when someone says something bad about you, and even if so, there are tools on all social media that allow you to in block and/or report people in some form. Think of it like walking around the corner of a building on the way to work every day and there's a pile of broken glass, and you step on a piece of it. After so many times there a point where it's your responsibility to know there's broken glass around that corner you walk past every day and avoid it, rather than blaming the glass every time and reassuring yourself it's not your fault.