From a safety perspective, kei cars have a lot going for them when compared with American-style SUVs and trucks. Their light weight generates less force in a collision, and their stubby front ends reduce driver blind spots. Research suggests that their occupants are equally safe as those inside full-sized vehicles.
At first, I was going to criticize the collision speed of the example study, but found ( ok, I say found, I mean I googled for 15 seconds ) that the average American collision is occurring at less than 40mph, so good to go there.
Second, I was going to comment on the relative safety of being in the Kei truck and being struck by the 2500HD... but that just goes back to the 'participating in the arms race', so feels... stupid.
So, overall: Thanks for providing this. It directly answers the primary concern of 'what if I hit something tho'. There are some other angles I could nitpick on maybe, but they all feel like a kind of 'consolation prize' to the argument.
One thing you also need to remember, is that the smaller car has a far smaller braking distance and is more maneuverable, so is less likely to get in a crash. The lower centre of gravity also decreases the likelihood of a roll-over.
Reminds me of a friend some years back. She was 4' nothing but insisted on driving a large SUV as it was "safer" in a accident. I'm taller than most but I prefer smaller vehicles like older Cherokees and Volvos so it's quite the odd difference.