Tell him he shouldn't play a game he doesn't like playing.
The same also applies to the OP. He shouldn't RUN a game he doesn't enjoy.
Though I find it odd that he can't stand 3e. My theory being, unless he is new to D&D, he had to have played a prior edition. Therefore, he would have probably liked that edition (most people like the edition they started on). Unless he skipped 3e, he would have tried it and most people liked it relatively speaking (at least didn't hate it, except for Diaglo). None of this matters, it's just unexpected.
In any event, the GM calls the shots on what to run, so long as he has players. So the game should stay 4e and he should keep running the campaign.
What the OP needs to watch out for is this:
couples in a group tend to vote together, so expect 2 votes for whatever his position is. This is because outside of the group, they will discuss and tend to come to the same conclusion (with the person who doesn't care as much deferring to the one who does, in this case, the guy).
The guy is going to make excuses to get his way. So he's going to complain about the campaign as well as the ruleset. Unless you're a really bad DM, you're not going to get anything from him that isn't just nit-picking to support his argument that he's not getting his way.
The safe way to get through this is diplomatically stick to your guns on what you're running, and suggest he sit this campaign out, and that he consider running the next one as 3e.