but each user (payer) can be objective about the provider which is censoring their own transaction. And since they all move away from that provider to avoid the censorship, then it has the net effect of taking PoW hashrate away from that provider
This objectivity is fine, except for the fact that the attacker is free to create an overwhelming majority of providers, such that moving away from one to another has no effect at all. There is a sybil problem here. You can attempt to mitigate this by making it expensive to become a provider, but then we regress back to the PoS security model, which no one wants in a new coin.
Sorry no. The users would have to be the attackers (assuming the users' cumulative hashrate far exceeds any attacker and remember I am targeting instant microtransactions so users' cumulative hashrate will be very astronomical with say 100,000 tx/sec). They decide the set of providers simply by choosing where they send their transactions.
Please also see
my reply to enet, wherein I explained what happens if 51% of the users are apathetic and willing to support abusive providers.