It just sets the humanity a few years back, The point is we don't have that many years left to stop irreversible change from happening. And the effect of his

It just sets the humanity a few years back, The point is we don't have that many years left to stop irreversible change from happening. And the effect of his actions (for example, in almost single-handedly reinvigorating an entire generation of rabid climate change deniers) may be with us for many years after he leaves office. If someone grabs the wheel of a car you're riding in, steps on the gas and sends it barreling toward a sharp cliff -- you don't just think, "this just sends us a few tens of meters further toward the cliff" (simply because the cliff is still a few hundred meters away). Nor would you describe any of your fellow passengers who seem overly concerned about the sudden turn in the state of affairs as "alarmist". Nor would you say "I don't like him, and I agree that rapidly approaching cliff edge looks linda scary -- but things don't always go our way." You'd do everything you can to grab the wheel back from him before it's too late. That's the situation we're in.