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.
If somebody would program a node to reject certain blocks, whilst they are valid when it comes to the consensus rules at height X, not much would happen. This node would just receive the next at height X+ 1 and would not be able to verify said block since he has rejected block at height X (and you need the hash of the block header at height X to verify the block at height X+1)