It's legal to create teams with offensive and vulgars names ?
No, it's not
If you find a team-user-arena name vulgar or offensive, you should report the team with a cheating report and the GMs should take care.
Just take in mind that sometimes not all persons thinks the same about this, so something you could find offensive could be OK for other persons
I close the thread, since this is something that can't be discussed in the forums and I think the doubt is solved