Trains should not be next to Cars should not be next to Bikes should not be next to Pedestrians. As for Kinetic Energy, The Diverging Diamond interchange is an incredible example of increasing the Safety with which Street and Highway vehicle traffic can exchange, by Reducing the number of Collision points that are -Allowed to Exist-.
20mph Bikes being next to 40mph Cars is a HUGE difference in Kinetic Energy, and dedicated Bike/Pedestrian routes are always the most pleasant to Bike on. Maybe not the most pleasant to Walk on! But obviously, everyone needs to get themselves and their goods somewhere, and compromises need to be made...
It would be fine if there was comprehensive bike infrastructure that allowed cyclists to never have to share road with motor vehicles, but we know that's not going to happen. As a result, drivers will see cyclists on the road and get upset and behave badly because they think to themselves that the cyclists "should" be using the bike infrastructure, not knowing that for part of the commute the cyclists have no separate infrastructure.
The cycling community would prefer the bikes be treated as equally deserving of space and accommodation by drivers, but it doesn't happen.