Amazing hyperbole, and a deflection from the real issues. You can fight against wrongdoing without actually advocating people being killed.

Right now, climate change is an undeniable fact, its causes well-known, and the evidence for it now part of everyday life. If anything, its effects have been underestimated to date, and 'non-believers' in it are either fools or acting based on morally repugnant principles.

Instead of this lazy deflection, you should suggest what you believe would be an appropriate attitude towards these people.