A little late chiming in here but I have the same problem on ALL my passenger grab handles. The odd thing is that on all vehicles on the market that use this soft touch plastic to elevate the aesthetics (that's every single premium brand I'm aware of) not one has been able to come up with a chemical formula that can withstand years of sweat and/or hand lotion etc. Perhaps I'm being a little hard on the R&D guys the world over but c'mon it's a handle for Pete sakes! People are bound to touch it from time to time. Granted it's amazing stuff but the hell with it...epic fail! Enough already, just cover the bloody things in dark leather or leave them bare. I've cleaned mine off and that's how they shall remain forevermore. They still look the same - black, and now they don't leave unsuspecting passengers wiping permanent black treacle like goo all over their clothing and my car seats.
Okay, rant over...