I'm not tarring anyone. I meant what I wrote, no more and no less.
I don't know about the frequency of such incidents, which is why I made no sweeping generalisations.
But the owner of dog in question did not appear to be the sort of nasty agressive individual that we tend to associate with rottweilers or pit-bull terriers.
Which still seems to leave a few unanswered questions in my mind.
There is a little-known reason why
some dogs see cyclists as a threat.
Unfortunately it relates to postmen delivering by bicycle. Every morning an unknown guy turns up at the pack's lair (which naturally sends a natural pack animal into high defensive alert). He knocks, rings or makes a noise at the door. The dog barks to warn him off 'this is my pack's lair please stay away'. He turns on his heels hops on his bike and rides off. With repetition over time the dog 'learns' that barking makes the threatening cyclist-man go away, so he really must be up to no good. It also reinforces the dogs hierarchy perception that it must be more dominant than the would-be intruder, since he always leaves when warned.
Then one day the dog suddenly sees a cyclist when out on a walk. The instinct to see off the threat can be very strong.
Of course the owner of such a dog should generally be aware that their dog has issues with bikes, unless it is the first occasion it has manifested itself in a chase. Mostly they will then avoid walks in places where there might be bikes. Desensitisation involving inviting the postman in to meet the dog and give it treats often takes a while, and requires a sympathetic and friendly (plus brave) postman. Most people don't even know why their dog developed the problem in the first place.