His worry is not unfounded. Beliefs matter. Beliefs affect ACTIONS.. actions such as: rolling back emissions standard goals, gutting research, allowing more coal emissions, opening up drilling in 11 states and the Arctic, disbanding the EPA emissions monitoring program, trying to remove the EPA climate-change research program, burying that climate report by releasing it on black Friday, trying to block California setting it's own emissions standards, etc... The US is leading the world with a clean environment DESPITE Trump's efforts aka his ACTIONS.. which are obviously based on his beliefs. Well.. his "beliefs".. who knows what he actually believes.