This means that Hitler didnt care for anyone. He was cruel and a dictator( a ruler).
Hitler liked no one and probably cared for no one.
He was so evil that he wanted to kill thousands of inasent people and even children.
What Hitler means by this quote is:
He is saying that nature is cruel so therefore he should be cruel. But nothing will ever get through his thick horrible skull. He would let millions of Germans die and still not care.
I hope I answered your questions and this is what you're looking for!:)