"All those biases that lead people to give time and money and thought to causes that don't really merit them waste not only time and money, but an exhaustible supply of moral fiber"
When you upvote a story on reddit about some issue you deeply care about, that tricks your brain into thinking that you have done something about it.
It is the same problem that announcing your goals makes you less likely to achieve them, because you already see yourself as a person who has accomplished that.
If people felt they had "done something" with the upvote, why would they feel the need to intervene for real?
One of the negative consequences of social media in general is that it can lead to very casual and even cynical views of how we relate to one another. Thus, what was meant to bring people together can actually make them more emotionally distant. If I see a hundred stories of trouble in the world, why would I take action on even one of those troubles?
"All those biases that lead people to give time and money and thought to causes that don't really merit them waste not only time and money, but an exhaustible supply of moral fiber"