Man is the greatest creature in the universe?
Because we are feeling creatures?
How the hell can Peter Graves be so sure of that? How much of the universe has he seen, outside of our cesspool of a world?
"outside of our cesspool of a world?"
Boy, you really should get out more and stop listening to conspiracy theories all the time.
As to how Peter Graves could know that about the universe. The answer is simple.
It's a line in a mediocre script written back when man's ego assumed we were the best beings in the universe. We aren't.