Re: what's unsafe about riding a bike, once bent ?
I can speak from a dual experience with a damaged heavy-duty (raleigh gran prix) front fork. I wasn't looking and hit the back of a parked car after swim team. The bike shop bent it back straight, but a few years later I/ wiped out on a tight curve at medium speed. Much to my surprise, the fork was bent again in the same way. This was highly unexpected - there was no apparent collision.
In other words, once the frame is bent in accident #N, bending becomes even easier in accident #(N+1). Of course, I can imagine that at some point, accident #(N+K) will happen all by itself which is a frightening thought.
I got a replacement fork.