By blocking the door if you detect an oncoming cyclist, you've created a new problem. What if it false-positives? What if it false-positives and your car is on fire? What if hackers find some way to fool the sensor?
In my mind, this is kind of similar to seat belts.
In case of fire, you can get trapped IF you cannot undo the belt, which does happen, but not always.
What I would do is, provide initial resistance to opening the door; but if you keep pushing, it opens, just slower.
As for the hackers, they can also control your brakes etc, so hacking thing needs to be solved anyways. Note that by 2020 that needs to be solved for every car sold in States, due to the CMBS systems being mandatory by that date.
