then both lotteries give you a 90% safety net, and you can afford to take the risky A in the remaining 10% branch.
I’m having trouble seeing how this works. Regardless of whether C is in the pool, I run a 5% risk of halving my wealth by taking the first gamble. I think the safety net metaphor only makes sense if the outcome can’t be worse than C, but in this example it seems like there’s a hole in the net I can fall through.
Policy debates are about opinions in addition to truth. Even if both sides only contain good rationalists who argue from true beliefs, they won’t necessarily agree on which beliefs matter more.