That sounds like exactly the sort of statistical analysis people tend to get spectacularly wrong. I'd be surprised if more than a single-digit number of people get shot while driving even in the US. For Europe, you probably need to express it in years/incident if you want to use integers.
Meanwhile, more than a million people die in crashes each year, and some 40 million or so are injured. Putting any, even small, additional obstacle in the way of help is bound to be a losing proposition.
This would essentially be a re-hash of the seatbelt debate, where many people were somehow convinced they could escape any accident by quickly jumping out before impact. That attitude lead to seatbelt laws, which were the single most important factor in reducing fatalities per mile traveled by a factor of 10 or so since the peak.
While I'm tempted to invoke some Darwinian principle, the damage wouldn't be limited to those making that decisions, but also their passenger, the next owners, etc, and possibly pedestrian victims of collisions.
In any case, I doubt it's actually forbidden right now. There are, after all, bulletproof cars. They just tend to be expensive enough to mostly discourage people motivated by Hollywood macho fantasies.