Where do we draw the line?
Is any level of effort short of maintaining an eyeball bursting maximum speed an affront to the poor dears on their way to the next tailback? What about using the crap that passes for cycle infrastructure in this country, should we be picking our way through the glass, fearful that our car borne betters will mete out punishment for any perceived delay we cause otherwise?
The biggest problem with handheld mobile use, regardless of mode of transport is that it distracts you from what you should be doing (paying attention to the road). Luckily, in the case outlined by the op, the user was utilising a mode of transport that a) kills vanishingly few people in the UK compared to the car despite the supposedly massive levels of irresponsibility displayed by it's users and b) doesn't allow high speeds to be attained/maintained whilst the user is engaged in this sort of activity.
F*ck me, if (as the op seems to suggest the hapless motorist is driven (ha!) to do) I tried to kill every motorist I saw jump a red light, drive on the pavement to get around a queue, use a mobile (texting in motion is a particular favourite these days, it seems) block a pedestrian crossing[1] I WOULD NEVER GET HOME. Motorists evidently aren't worrying about giving each other a bad name - and some of the common behaviours I've listed there ARE ACTUALLY ILLEGAL.
This hand wringing over whether irresponsible cyclists will get you a punishment pass, or similar is bizarre. Obey the law, ride sensibly, and you could still get one anyway, because you ride in the UK. Even if you don't experience malice, my experience of Manchester suggests that inattention, impatience and indifference can be every bit as dangerous, and are far more prevalent.
[1] Most recently, near me, blocking a wheelchair user from crossing for 3 changes of the lights. Drivers stared fixedly ahead when we (the wheel chair user, a passing pedestrian, and I) suggested that they were, perhaps, being rather selfish.
