Honestly, the fact that they are even available for testing means that some criminals will use them, even if they are outlawed.
As to the specific points raised:
It discussed issues such as letting criminals shoot while the car drives (silly in my opinion, apparently they haven't heard of "partners" or considered requiring such cars have a police controlled "slow down" command),
Slow down command won't mean a thing when the criminals rip out the necessary parts to make it moot or reprogram it to do something - ignore the command, do the opposite, or even blow up the vehicle.
the use of such vehicles as guided bullets (safeties again should stop this), and loading it with explosives and using it as a guided missile. This last concern is the only one that I considered a real issue, but even that is not significantly more dangerous than loading up a regular van full of explosives with a timer, then setting the timer to explode before you leave the vehicle next to a school, etc.
True, aside from it being a "guided" missile - just set a target in the GPS and off it goes....again, the potential is there and criminals won't allow it to stop just because of a "slow down" or "stop" command. They'll figure out a way to override that before using it.
And again, if they really wanted to do it the technology is already out there and nothing is going to stop them from using it if they really wanted to.