I too have seen straight actors playing gay roles who made me cringe, and gay actors playing straight roles who made me cringe. So perhaps the conclusion to be drawn is that while it's always called acting, sometimes it can also be called BAD acting! : )
May I also assume that you've seen straight actors playing straight roles that have made you cringe, and gay actors playing gay roles that have made you cringe? And actors that you had no idea what their orientation is making you cringe as well?