> Most importantly, it ignores the fact that proprietary software in cars is at least equally, if not more, dangerous.

To me it seems that he is suggesting that the proprietary software can be more dangerous than open source one. So from there you can infer that he believes that open source software can be more safe than proprietary one.

If death(proprietary) >= death(OSS) then !death(OSS) <= !death(proprietary)