Why would anyone buy Steem if it could be forked away?

That is so reductive I dont even know where to begin. A sister fork must freeze all the stake being used to attack the chain. The reason you buy Steem in this scenario is because Steem is a blockchain that defends itself from Sybil attack. To make the claim that "anyone could have their account frozen" because the attacking parties are being neutralized is absolutely absurd. Dont attack your own investments. Sorted.