About defending capitalism (and not billionaires - who more often than not abuse this system). Some of us lived in other systems. And we understand any other system is way way way way worse.
There are however a lot of problems with capitalism and should be held on a very short leash. Or else monopoly happens. The most effective actions to keep capitalism at bay: strong anti-trust laws, strong worker protection (this includes a lot of stuff), wealth tax.
And be aware there are many flavours of calitalism. Most commonly people in USA are the most extreme where you have really "long leash". And people see such capitalism as failing and want to replace whole system.