I had a friend like this that I used to roll with back before he moved. Let me tell you, don't try and change him, let him do his thing. I'll tell you why.
My friend, we'll call him "T" was also very polite to fattys. He could spit some game (but it was mostly nice-guy game) and he got laid quite often. Infact, his lay number is/was nearly double mine, but my theory was simply because his standards were far less than mine.
Anyway, he became really handy at times. Have you ever been in a situation where you were macking on a hott girl and then her fat friend tries and CB? I used to have that problem, but not until I met "T". This guy was a "player" but he would seriously fvck anything with two legs, especially when he was drunk (which we almost always were). It was usually me, my friend "R", and my friend "T" and we'd roll like the 3 amigos. The glory days when we all used to party hop and get laid every weekend.. man, I miss those days. We actually used to make fun of him for being a "chunky chaser" but he didn't care. He wore the title with pride. In fact, his forte was chasing big woman or really older woman (he'd have a girlfriend and usually try to fvck her mom too, often times, he was actually successful). Totally went for the insecure girls that needed some "lovin" by every means of it. Anyway. You may see it as annoying and polluting your image now, but it's not you. Most fat girls have some hott friends, and vice versa. Use him to your advantage. If a girl ever clinged to me that I didn't like I would often just introduce them to "T" and they were off my balls instantly. He sarged, and he sarged HARD. Very persistent. Almost to the point where it was creepy. But he still managed to get laid. I actually miss him. But anyway, let your friend do his thing man. Look at it from outside the box. He may come in handy one night.
-Scars