Re:
I'm afraid the OP's post is a perfect example of stupid people riding bikes.
I did a sportive on Sunday, and while carefully dealing with heavy traffic, I was undertaken by another cyclist. I did not know he was there, he did not give me any 'passing on your...' warning and he missed my bars by a couple of inches. When we got going I overtook him again. Then at a very busy, slow junction he cruised past me and straight out onto a main road, I overtook him again and then he and his pal overtook (or maybe undertook) a whole stream of slow traffic (being held up by other sportive riders) by riding along the pavement. Both riders were over 60, so really should have known better, and I was tempted to ask them if they would be moving on to jumping red lights and smashing car wing mirrors next. :facepalm:
Idiots are idiots, regardless of how they choose to travel.