You can boycott the game if you want. But personally (and I say this as someone who is: a) very politically active, engaged, and involved; b) a big proponent of gay rights; and c) not at all interested in Shadow Complex specifically), I find the idea of boycotting an artistic product because of the political views of its creator (or, in this case, tangentially involved in the creation, at best) enormously silly. I understand that this is an issue obviously near the hearts of a lot of people, but it's just not an effective way to express that. If you're going to successfully manage in the course of your life to appreciate any form of artistic endeavor, that is going to on some level necessitate dissociating the artistic work from its creator.
It's one thing if the product itself is expressly wrapped in abhorrent political views, but that's not the case here. And similarly, while I detest the political views of Johnny Depp and Mel Gibson, they're damned fine actors and I'm not going to deny myself the ability to appreciate their artistic talents unless they are being applied in a work designed to promote those views. Eric Clapton has endorsed fascist and racist views, but I'll be fucked if the dude can't play the guitar; I'm going to continue to listen to and appreciate his music, and I doubt most people would be willing to boycott Rock Band or Guitar Hero over him (and nor would it be sensible to do so). Koichi Sugiyama is a nationalist and a historical revisionist who has expressed disgusting stuff; his music is still wonderful. And I listen to a ton of classical composers who I'm very certain have, having been on the wrong side of history, held hateful viewpoints. Whether in film, literature, music, or gaming, you just have to separate the artist from the art and be willing to let that art stand on its own merits.
The suggestion made to donate an equal amount of money to a charity that's pushing for the right kind of political action is a really good one, and I hope people just take that productive and beneficial route instead.