Don't ban people just because you are too lazy to work out how to use the technology that prevents people typing anything using profanity
You were banned, by yours truly, for overt racism. No need to quote it, as we both know what you said.
As for the rest, I would first like to point out the legality of things, which is that you are SOLELY responsible for what happens to/with your account. It is not incumbent on me to try and determine whether perhaps an ex used your account.
Also, along with what Ren said, we prefer mature, adult reactions, along the lines of "Sorry, I made a stupid remark," or "Yes, my bad, I hadn't bothered to ask permission to take that car." But "It was my kid brother who stole that car," or "Someone else made that racial slur," as you've noticed, doesn't really get you anywhere.
In case an account actually does genuinely get compromized -- and this goes for all -- you contact the staff immediately, and we will try and remedy the situation. However, making threats, and yelling we can't stop you, again, horrid set of choices on your end, and quite indicative of us having made the exact right choice banning you.
EDIT: Perhaps in abundance, but you sharing your account is, in itself, a violation of the TOS:
"You may not use anyone else's Account at any time and you may not allow anyone else to use your Account at any time. You are responsible for all activity occurring under your Account, including all activities or transactions conducted through the use of your Account."