I've done nothing of the sort. If I add a rule to my client that it quietly drops blocks that are over 250Kb, what have I done to you?
Nothing, but you've kicked yourself off the network (until a majority of mining power + a significant amount of full nodes on the network implement your rule too.
No, I haven't. You don't even know that I dropped your block. I can participate as a node just fine, just not as a miner. It's a balance of forces.