Not all of them, but a few bad apples spoil the bunch. If someone drops a turd into a barrel of drinking water, we don't say that it's 99% clean water and 1% turd. And in the case of humanity, the percentage of turd is double-digits.
The real tragedy is that people have always (collectively) been selfish, greedy, short-sighted, irrational, violent and destructive. It's how we're wired. Instinct drives us that direction because those traits have been naturally selected for over millions of years. Apparently modern homo sapiens was the fittest to survive.