There is a steem-abuse channel in steemit.chat for appealing a decision. I think that should be the first step.

If it is the case that the 'police' are not being fair or reasonable themselves, I think the user should appeal to the community, present their case, and hope that someone with Steem Power will protect their account for a while using autovotes. If they act abusively in any way, such protection should be revoked.

I think we will a decentralised system of policing like this emerge over time.