OK Jon. Rather limited experience but have owned my own boat for two years now and cruised for something approaching 1000 hours (all north of Braunston). Coventry canal, T & M, Shroppie, Llangollen. Have had no problems at all. Saw a group of youngsters - in hoodies - congregating near the Ash Tree bridge in Armitage (on T & M) at Easter. My wife ducked for cover, but I and the lads just had a pleasant chat as I hovered before the bridge hole waiting for an oncoming boat to clear.
Not saying that there are no "bandits", but do feel that the issue is blown up on the towpath telegraph.
Oh, and as I rapidly approach retirement I guess that I fall into the category of the "more elderly boaters" that Gaggle refered to (Thanks, mate)
Graham