A 4.16 ratio is not at all a surprising number. If anything, I'm surprised it's not even higher when you consider that Baltimore City and Washington DC went roughly 8:1 and 9:1 for Kerry.
D.C. and Baltimore are both predominantly black. Philadelphia is predominantly white (74%). Since blacks vote Dem about %90 it makes sense in those cities but not in Philadelphia. Agreed Philadelphia has a higher than average gay population, I doubt it tends towards about %50 which would be needed for it to account for a 4:1 ratio.