Sometimes I wonder who it is run by, but I think the diversity of opinions is accepted by imgflip itself. I don't think the opinions are balanced according to the general populace, though.
i'm pretty sure there are more righties than lefties (or at least the righties are more vocal)... but i see some anti-right stuff featured that leaves me scratching my head it's so extreme and then i see some anti-left stuff that's pretty mild that they won't feature. mods definitely have an agenda beyond letting good memes be generated!