Where does Riot draw the line on vulgarity?

Calling someone a "c - - -" or "mother f - - - - -" or "r - - - - - - - piece of s - - -" is cool in Riot's book and players can carry on their merry way, but calling someone a f-a-g for griefing you in your jungle grounds for a 14-day suspension & honor termination? I want to know, where does Riot actually draw their line for tolerance of behavior in this game?
Report as:
Offensive Spam Harassment Incorrect Board