> "Defeatism" is yet another shibboleth for people who refuse to accept reality.

Sometimes you'd be right, as some people use this as a shield to do whatever naive thing they want, and build sand castles. But I don't think this is the case here. Society needs some level of potentially useless effort, otherwise the things that are barealy possible are never attempted because they are so close to the line.

There's also plenty of causes for which people can mobilize themselves, we don't all need to jump on the ones that are highly likely to succeed.