Is it time to start calling out bad cyclists?

you: i used the horn to make a point

highway code:
112

The horn. Use only while your vehicle is moving and you need to warn other road users of your presence. Never sound your horn aggressively.
(http://www.direct.gov.uk/en/TravelAndTransport/Highwaycode/DG_070289)

so maybe he flicked the vs at you as if you had done something wrong because you did do something wrong

also that RED find made me do a big lol

Incorrect. Clearly they were not aware of his presence otherwise they wouldn't have been on the wrong side of the road en masse.

He just wanted to make sure they weren't deaf as well as blind.