Minecraft does not ban users for profanity. The list of ban offenses is currently:

Hate speech, sexual content and soliciting improper contact, real life threats, exposing the personal information of others, posting links to malicious software, impersonating staff, cheating/exploits (this includes anything that would negatively affect another person’s gameplay experience), general commercial spamming

Profanity is considered the responsibility of specific server moderators since it's a low-level offense that's virtually impossible to police in a game like Minecraft. They're trying to avoid the notoriety recently obtained by Roblox for being a place for adults to exploit children.