Sorry this is a week later, but wanted to be sure I passed along this information with reference to the CDL Manual. It was suggested in the email discussion to update the CDL manual. In fact, Maryland's CDL manual is modeled on the AAMVA manual (American Association of Motor Vehicle Administrations), and the sections mentioned in the email discussion regarding bicycles are actually taken word for word from the AAMVA model. There is a new version being printed this month with changes as a result of national model changes. I double-checked before sending this, and the new version of the CDL manual will have the same language on bicycles.
Because the verbage is basically handed down to us, any updates to the manual are definitely not something that could be easily changed -- likely, any request for changes would have to work their way through nationally. It may seem unfriendly for trucks to blow their horn (or tap it lightly) at bicycles to make them aware of a truck behind them (getting ready to pass), and for bicycles to be listed as a potential hazard to trucks, but certainly the national model to teach truck drivers how to drive safely would not suggest harrassment of bicycles. Both of these sections mentioned are from the section on "Driving Safely" -- with the first under "Communicating Your Presence" and the second under "Seeing Hazards."