Don't Antagonize the Rich
Leftists often complain that the rich are not paying their fair share of taxes, if they pay taxes at all. After all, there is an entire industry of tax lawyers dedicated to ensuring that the rich don’t have to pay their taxes, as is portrayed in the John Grisham novel "The Firm". Implied in these complaints is often the assumption that the poor are saddled with an unbearable tax burden, supplying the government with the funds to build and maintain infrastructure and services that the poor don’t use, which is rather silly considering that in many western countries the poor don’t pay taxes at all. The majority of the tax burden of course falls upon the middle and working classes.
I am not an economist, but I can think of at least one reason why it might actually be a good thing not to overburden the rich with taxes, as long as international free trade exists anyway. It’s always better to have the rich people (along with their business and their industry) in your own country rather than somewhere else, and if a rich person thinks they might make more of a profit in another country, they may just pack up and move there, taking their money, the business, and their industry with them.