I know there are lots of everyday moments of humans being kind to each other, but do you have any good examples on a wider scale to counter that capitalist realist idea?

I usually try and invoke the fact that humanity for hundreds of thousands of years lived in tribes where they had to co-operate or they would die and that "human nature" is just the product of the system under which you live, but are there any better examples you've found to convince your lib acquaintances?

I feel like one of the major hurdles towards getting somebody to become a leftist is the idea that humanity can, if organized democratically and if properly educated and with the right ideas of solidatory instilled, create a better system than the capitalists or technocrats have created. It's easy to look around and superficially see everybody as bumbling idiots or greedy assholes, particularly if you're socially atomized and apathetic, and so conclude that the working class, if left to it's own devices, would infight and crumble.

Or is this just one of those axiomatic things where if somebody you know believes it, it's very difficult to make them not believe it through historical examples unless they do major soul searching after a personal crisis?