That would actually be pretty easy to do. See that frizz around the Paki's head? That would be somewhat difficult to get in there and not look too weird. However for real professionals with good filters and skills, not impossible.
Look at the right side of his jacket at the bottom. That looks unusual to me, almost filled in with a darker shade.
If I had to pick one of the two who don't belong in that photo, I'd pick Hussein. But, like you said, who knows?
They are all fake, ALL of them, the ones from grade school, Occidental, Columbia, Harvard, and on. All photshopped. Damn, he needs a full time staff to handle all the photoshopped pictures. Sometimes the paranoia really irritates me. When and if they photoshop it is to make him look better, why in the hell would they want to stick him on a couch next to a gay Paki and they give it to the NYT. It defies logic. I will leave you to your delusions.