I would point out to the cyclists that in the days when the Kennet and Avon was a series of muddy puddles, with here and there a patch of navigable waterway, it was very largely walkers who kept the path open. It was also a safe place for small children to learn to ride a bicycle. Now those same walkers are being driven from the path by the antics of some cyclists, and children on two wheels are no longer safe there.
Remonstration with the new "kings of the towpath" is regarded as politically incorrect, and anyway will be met with a mouthful of abuse. I speak from experience. The mass trespass threatened by the cyclists is nothing new. In the days when a licence was required (and if my memory serves correctly it was not pounds 3 but pounds 1) it was ignored, and notices reminding users about it were defaced.
The long-term future of this canal is still in the balance. Nearly all other users of it are keen to help. Why are cyclists the exception?