I perhaps haven't expressed the position well however, "naive" isn't a slur, read "simplistic" if it helps, it's philosophy on the level of someone who has not demonstrated cognisance of the basic sources and hasn't addressed the obvious counter-arguments.

The mainstream Christian theology is that leprosy, and such diseases came in to the world after, and as a consequence of, The Fall. That if we'd chosen God's way we wouldn't have such things.

>So God inflicted leprocy on humanity //

God created a Universe with free will for man rather than creating a fancy automaton. Mankind chose not to follow God's precepts, the consequences being that disease, pain and suffering entered the world.

It's like if I serve you a hot drink. You can choose to cause pain and suffering with it - throw it at someone, say - or you can follow my instructions to sip it slowly, let it cool and enjoy it, share it. I can't serve you a hot drink without the possibility that you will abuse it, unless I make you into a "hot drink robot" with no free will.

You could couch that as God inflicting the possibility of suffering in order to allow the possibility of beauty, love, passion, humanity.