Dangerous because they attract the wrong people who ride them.

A friend of mine is a nurse in a neurological ward. She says the other nurses call people like that donor-cyclists.

I also used to ride, mainly touring in the UK and Europe, and I largely agree, but there's also an irreducible risk of getting killed or maimed by other, larger vehicles, regardless of all the precautions you take. I was extremely cautious and well-trained, but still had a couple close calls. Mitigated risk is not zero risk. And, as they told me during training, when you're on a motorcycle, the crumple zone is your own body.

The same is true of bicycling, but fortunately there are some good bike routes where I live where you're mainly separated from traffic.