Personally, I never understood why he was hated for that ! He got a red card for it, so it's all in the rules.
My personal reason was that, like 80,000 others in the stadium that night, I was desperate for Ghana to go through and this denied them the fairytale. Admittedly Gyan had the chance to win it from the spot anyway but couldn't finish it. Luis spent a lot of time that night prancing around and diving/rolling all over the pitch as well which grated on me. Now that you see him up close (well, not literally, but take enormous interest in him) you can tell that what he does is do
whatever it takes to win.
I like that.