> The optimist keeps trying to do something even as the evidence piles up against it. He calls someone pointing this out a pessimist.

If someone insists that something would work even when the evidence is clear that's borderline stupid. But let's look at pessimism and optimism in relation to something unknown. An optimist would continue trying even if they fail multiple times, they continue trying until they either succeed or find enough evidence that it won't work. While a pessimist won't even try once, or give up pretty early.