It must be galling for motorists to discover that they have to share the road with a form of transport that does not pollute the atmosphere, occupies very little space on the highway, and moves at an annoyingly low speed (i.e. within the speed limits).
My own experience as a longtime cyclist is that most motorists are considerate road users and give cyclists plenty of room when overtaking.
The trouble is that there is a prejudice against cyclists by many car drivers who assume that their rights trump slower road users. Somehow horse riders do not come in for the same vitriol, but the drivers of farm vehicles do.
Narrow roads are a hazard and the lack of dedicated cycle lanes in large towns and cities in the UK puts cyclists at risk.
There are idiot cyclists, just as there are inconsiderate drivers, but reducing car journeys and increasing the cycling population makes environmental sense.