By cursing and effectively baring the party from completion I believe it falls under the anti-harassment clauses.

Specifically these two I believe.

Prohibited Activities:
3.2 Disruption. You may not in any way disrupt or interfere with the Game experience of other players, including the disruption of Square Enix's computers and servers.

3.3 Profanity and Offensive Language. You may not use profanity or any language that a reasonable person would find offensive. The Game is for players aged 13 and older. You agree to behave accordingly.

Here is a link to the full ToS if anyone would like to see it,

http://support.na.square-enix.com/ru...2&tag=users_en