Many community managers are either too slow or too fast to remove antagonistic members. They either remove the antagonistic member without fully realizing the role this individual plays within the community, or they spend copious amounts of time trying to convert the antagonist into a happy member.
Online community guidelines detail the types of behaviors that are and are not appropriate on your community. They include things that some might consider obvious, but they also include items that are somewhat unique to you and your community. I liken an online community to a country. Each country has culture, laws and social norms that make it different from every other country.