Facebook does not tolerate bullying and say they will remove bullying content when they become aware of it and may disable the account of anyone who bullies or attacks another. They have a set of community standards that they adhere to and it states that they will not tolerate bullying in any shape or from. You can report bullying on face the report links which appear near the content itself, as 3 dots and will give you an option to hide or report the comment or post. they will investigate and let you know their outcome. You may want to read their help pages on bullying.
Even trolling can be seen as a form of bullying, which is why it is so easy to be caught out by these people.