Blocks aren't valid with double spends in them. You are saying the miner makes an invalid block by the rules in order to have a double spend transaction and the

Blocks aren't valid with double spends in them. You are saying the miner makes an invalid block by the rules in order to have a double spend transaction and then mislead the spv client with that information? I'm not making the argument that relay nodes are useless just that their security is being over stated, it catches this particular issue.