This falls under the category of "is it right to give someone spreading something hateful a platform?" In light of recent tragic suicides, brought about at least in part by reported anti-gay bullying, this seemed important to post.
If you don't support the statement rapper 50 Cent is making on his (very adult) Twitter feed (even if the "LOL" is meant to convey some kind of implied sarcasm), then you should not support his music, movies or brands.
Celebrities have platforms and can make a difference. By posting this to his 3.3 million-plus followers, he's not using that platform for good.
Update: 50 is back on Twitter Friday, responding to reports of his previous Tweet. He doesn't appear happy with the negative fallout, saying in one post, "Some how they turned a simple joke about oral sex into a anti gay statement. I have nothing against people who choose and alternative life."