The funniest thing is he has no problem with Turn Undead pushing, or with pulls; his only problem seems to be when I use an attack that pushes as an effect on a rather large creature, or when my Combat Challenge stops a large creature from moving (because he points out it wouldn't be enough of a strike to stop them - missing entirely the fact that they stop moving because something just hit them and drew their attention)
That totally fits in with the guy who chimed in a while back with "Reroll as arcane or divine, and the problem goes away".
The issue is a GM who doesn't believe that a martial class can do certain things, and doesn't want to be convinced otherwise. Whatever tweak of personality that leads them to feel this way doesn't apply to magic at all.
However, I do find it interesting how the GM's sort of existential anger with "but fighters shouldn't be able to do that" seems to be leading to you being a fairly effective Defender after all -- if nothing else, you guarantee that a good amount of his mindshare in tactically moving the monsters is getting used up on how to 'keep you honest'. So, yeah, kind of dysfunctional, but it works?