What happens if he refuses to accept that block, and another miner creates a block without that transaction, and he accepts that. Won't this create a soft fork, and it will be up to other miners to decide which fork to run with. My guess would be that most nodes and miners won't want the overhead of checking transactions, so it would need to be an automatic check in the core software. Spammer support seems to exerting an influence here, and that is a bit concerning.