I think this whole side thing is silly. If you actually read the original fic (something I haven’t been able to find after I read it once more than a year ago) it paints Celestia in quite unfavorable light. Of course people would like the Lunar Republic.
It’s like asking (most)American’s which side of the American revolution they’d be on. The fucked up lower level educational system usually instills this thought that there was this oppression within the colonies when none really existed. So, as I said before, silliness :T