FrogReaver
The most respectful and polite poster ever
Oh, I see. Sorry. You're asking about the if the first time this came up, the situation were reversed. That's a little harder. I think if the weirdness of it struck me, I would allow the disengage in that instance and then have a post-session discussion about it to let the table decide how we wanted to play it.
I wouldn't. I'd just allow the disengage unless I thought it was really nagging at someone.
In the OP's case I would rule against him because I dislike the notion that the player feels he is entitled to an OA so much that he would push for the enemy to not be able to disengege.