The war of words over the decision by Vanguard to not participate in industry ESG initiatives is heating up. "Our research indicates that ESG investing does not have any advantage over broad-based investing," CEO Tim Buckley said in a recent interview. Vanguard, the world's second-largest asset manager, has been a target for activist groups, who say the company should do more to phase out investments in energy companies that are too fossil-fuel friendly. Vanguard has $300 billion invested in fossil fuels.

The comment came after Buckley previously had withdrawn Vanguard from the Net Zero Asset Managers Initiative. It has garnered $59 trillion in commitments from corporations around the world and commits companies to comply with the Paris Agreement's objective of net-zero greenhouse gas emissions by 2050. Such a commitment, Buckley said, is incompatible with the fiduciary duties of asset managers such as Vanguard.