If he had muttered the "n" word in a private moment of frustration, would the PGA and the rest of the world be so sanguine? I think not, but where it's laregly socially unacceptable to be racist, it's still quite OK to be homophobic.
And whether or not he consciously feels homophobic in his conscious mind is irrelevant if he's normalizing that term. I completely agree that a sincere apology is a nice start but if he doesn't really know why he said that (let's take him at his word) then what effort is he putting in to figuring that out and making sure it doesn't happen again?
That makes me really sad that you were driven away from a sport that you enjoyed. In a dominance hierarchy, those lower down the pyramid are expected to take abuse stoically from those with more social power. I think that's a large part of why so many people brush this off as no big deal, but it's still maddening.