Hypersmurf
Moderatarrrrh...
But you have to concede that the opposite is also true; it doesn't state that you choose the direction.
It states that there is a restriction on the direction you can push someone, and tells you what that restriction is. If there was a further restriction on the direction, that's where it would be stated, and it isn't.
Determine whether the square you want to push someone into is farther from you or not. If it is, you've satisfied the restriction on the direction of a push.
Someone is adjacent to me, to the north; he is 1 square away. If I want to push him SW, SE, E, or W, he will end up 1 square away; this does not satisfy the restriction on the direction of a push. If I want to push him NE, NW, or N, he will end up 2 squares away. This is farther from me; it satisfies the restriction on the direction of a push.
Your DM is introducing an additional restriction, that says if he is north of me, I can only push him north. This is not found anywhere in the rules.
It doesn't say I may only push targets who are wearing red cardigans. Neither does it say I can push targets who aren't wearing red cardigans. But if I weren't allowed to push non-red-cardy-wearers, it would appear in the restrictions on Forced Movement or on a Push; I don't need a specific statement that non-red-cardy-wearers are valid targets in order to know that the restriction which isn't written anywhere isn't actually a rule.
-Hyp.