Leon Cooperman called out Elizabeth Warren for ignoring the charitable and societal contributions made by America’s wealthiest entrepreneurs, escalating his war of words with the Democratic presidential candidate.

“However much it resonates with your base, your vilification of the rich is misguided, ignoring, among other things, the sources of their wealth and the substantial contributions to society which they already, unprompted by you, make,” Cooperman, the son of an immigrant plumber, said in an open letter dated Oct. 30.

The billionaire, who bootstrapped his way from the South Bronx to become one of the deans of the hedge fund industry, wrote the letter in a response to an Oct. 23 tweet by Warren that said he should “pitch in a bit more” so that others have a chance to succeed at the American dream.

Warren singled Cooperman out after the investor told Politico that while he believed in progressive taxation, he has fundamental disagreements with her approach. In his response, he details his philanthropic efforts and those of other billionaires, quotes Internal Revenue Service data on the higher tax burden of bigger earners, and cites experts who question the feasibility of Warren’s proposed wealth tax, her main means of raising money for the ambitious spending programs she supports.

He closes by asking Warren to “find common ground” rather than “firing off snarky tweets.”

Cooperman is not a prolific political donor, and he has mostly given to Republicans. In 2016, he supported the presidential campaigns of Jeb Bush and Marco Rubio. He also gave $1,000 to Hillary Clinton that January, but her campaign refunded the donation the following month, Federal Election Commission records show.

This article was provided by Bloomberg News.