I was a motorcyclist for many years, and I was pretty reckless at times. Certainly, open-road speed limits were something I paid scant attention to. Many of my motorcycling mates were similar, but I'd say we were a relatively small subset of motorcyclists generally. I gave it up after I was taken out by a car driver in a low-speed crash (<30 mph) from which I'm still suffering the after effects 18 years later.
I won't associate myself with Flatus' comments, but I can understand why he might have come to that viewpoint. Like anti-social cyclists (but more so), andti-social motorcyclists are highly visible, noisy, and so blatantly ignore the law and accepted standards of careful riding that they engender very strong reactions from others. The tendency to generalise is always a problem, but there's no doubt that there's a larger proportion of nutjob bikers than car drivers - bikes are cheap, are very, very fast, and have a culture of speed and risk-taking which doesn't apply to most Ford Fiesta and Nissan Micra drivers.
My brother is a full-time advanced motorcycle instructor, and he tears his hair out at the antics of so many bikers. Yes, a number are keen to improve their riding and pursue further qualifications, but few of them ride supersport 600/750/1000cc bikes, which are the largest part of the UK market.