Well there is easy trick to tame these guys ,

1) Build 2-3 walls or simply a room enough to fit a diplo so other carnivore cannot attk it while u are taming ( have w window or something from where y can feed it) ,

2) Once u loose aggro, Diplo will continue to attack ur walls which makes them Hungry fast Than U loosing aggro and they wandering around.

If this goes Well up it so other can Try it out too