When Alice executes the double spend, bittrex won't shut her account down, they will put the wallet on maintenance. If it happens more than once, the coin in question gets delisted. There is plenty of precedence for delisting PoW coins that are double spent through 51% attack. Alice can then move to a new exchange.

Dan's 51% hashes don't censor Alice, it kills the coin.

You are struggling to defend Hive account@dan, but he's not even here defending himself. He's hiding because he knows he is wrong on this issue.

Check this out: Na na na na na na -- Hive account@dan you are wrong!

See? No Hive account@dan.