On reflection why the heck do they have to be Bengali?
I'm going to jump in on his defense. Yeah, he probably want to sleep with a girl who looks a little bit like the girls he used to have a crush on in his teens. That's not racist, if he grew up in Alaska he might be interested in an Innuit. Your first punt, you wanted it to be with a girl you fancied of the type you wish you could sleep with. That fair enough. Practically, if he was taken to a massage parlor, instincts would kick in and he'd plump for the first girl he saw. But nobody wants to sign up for that as a first time experience (not without 14 beers first).
Secondly, probably more importantly, guys from Bangladesh on average have much smaller penises that people of western decent. We've all seen the porn, and read the amusing news stories about tiny condoms in India. He may just want to not be laughed at by a prostitute over the size of his majestic rosewood erection.
See? I both supported him, and insulted his tiny dick. That's profiling, that is.