There's a Canadian billionaire who is famously always donating to hospitals and suchlike. He's had tens of thousands of employees for decades and I've never heard anyone say anything bad about him.
I know another billionaire in Vancouver who isn't known for donations. Actually most people don't know he's a billionaire. He is generous though; he just insists on being anonymous when he gives large amounts.
I suspect the issue is less "billionaires are horrible people" and more "the highest profile individuals from any group tend to be the narcissists".
The argument that, for the most part, you need to extract from and exploit others to get to this level of wealth is relatively strong and has correlates with other negative behaviours I would say is the core issue at play here.
Turns out that taxing their wealth is an intervention.
We need to do it if only for their own good to save them from the pressures that cause them to act increasingly antisocial.