He's right you know.
Very nice, bright colours look great too.
As far as a big cassette goes, I've got an 11-34 on my bike and I've never once thought it looked strange & it's an aero bike..
My girlfriend's dad's bike however...
He's running an 11-42, on a Time fluidity 2, not an aero bike as such, but boy does it look out of place on a road bike.