How would one relay a raw tx double spend to a node that accepts it? All of the pushtx sites reject the tx as a double spend. Would I have to run my own node through bitcoind? How would one do this?
You will have to have custom software that can broadcast the transaction for you. Basically any and all nodes and transaction broadcast services will fully validate the transaction before it is broadcast. One part of that is checking for double spends, so you will need software that does not do this. AFAIK, there is no publicly available software that does that, so you would need to write your own broadcaster.