Or tell them you have IBS.

I HATE wheelsuckers!! My peripherial vision is awful and I am always worried I will be unpredictable and cause a wreck.

DH is incredibly strong and without fail we get several wheelsuckers on any organized ride. The exception to my disdain is the wheelsucker I had at the Katy Flatland who took the time to introduce herself and ask if I minded her riding my wheel. A polite wheelsucker is not a problem for me.