I think classist and elitist the first idea.

Whitelist: do not downvote if the user is on itr

The more control, the less freedom, the perfect formula for steemit's failure, with reference to history.

Bidbotted percentage: downvote only if bidbots represent x% of the payout.

minimum payout : only downvote if the post has reached x$ of potential payout

Number of words / characters, only downvote if the post has less than x words / characters

The request lacks to vote negatively on account as the positive vote does, it only does it following a trace of another, it takes away people's own criteria.