Hello !
I think the answer would be...
The last option, "The Nation has to go through significant changes to avoid such tragic wars in the future."
I hope I was able to help you out ! :DD
The phrase, a decent respect for the opinions of mankind, was intended to convey a respect for what mankind thinks. Opinions are biases indulged by mankind inside their thought-matrices. Mankind is the species known as Homo Sapiens Sapiens.