Hogwash.

I'm in no way an advocate for always riding on the sidewalk but whether or not you're allowed to varies depending on local laws. Here in my town, the law states it's perfectly okay to ride on the sidewalk anywhere outside of a business district (ie: downtown). There are a few sections of my commute to the shop (really tight multi-lane roads with no shoulder) where if I didn't ride on the sidewalk, I'd have to get off and walk.

If some dickhead ever tried to clothesline me as a result, I'd be sure to mercilessly ruin his day.