Would any of us understand this picture if it weren't a white male destroying the earth? What if the picture were a native woman, or an African American woman? Would it make sense to us?
In hierarchies, we are programmed to think that the top group, in this case white older tall able-bodied males, represent everyone. Also, since we know they have the most power, to put one in a cartoon like this makes sense.
Notice how political cartoons represent the powerful hierarchy conservators as similar white males, and that when the political party that most believes in conserving hierarchies, Republicans, are pictured as elephants, they are usually wearing the suits typical of white males.