It's interesting that, in a way, Thanos was right. Sure, many countries simply mourned after the snap. But in places where people were fighting every day over scraps simply to survive their lives improved considerably. After everyone came back, they weren't willing to relinquish those gains. They had been doing better. Maybe the Flag Smashers should have called themselves Children of Thanos.
The problem with Thanos isn't his ends, it's his means. Of course conflict arises when resources are scarce and reducing "demand" to relatively increase supply CAN be a solution. That doesn't make murdering half the universe any better as one of the worst acts imaginable.