One of the justifications is futility. You say,

你可能担心你的捐款不过是徒劳
well these poor people in these less developed countries--

发展中国家那么多的穷人
you really can't help them anyway because it'll all get lost or

你没法帮助每一个人的
the population will increase and there will be more dying people.

他们会过度生育从而带来更多的死亡
Anyway, he dismisses that; you have to read it.

但是作者驳斥了这种观点你要读一下
It's a rationalization that we don't spend too much money--

我们这种行为是合理的
too much time on. We don't dwell on it

我们不愿意花时间也不愿意花钱
but we assume that it's futile and so we ignore it.

我们认为一切都是徒劳因此我们有所忽略
Another one is that it's

另一个原因可能是
very difficult to be a truly moral person.

有德之人是很难当的
I would have to give--if I really thought about what was--

一个有德之人当他知道情况那么糟的时候
the terrible things that were happening,

他可能会一下子