This is a very long thread, I should ack that I have not read all the posts but here is my opinion anyway.
First of all how do we define what "evil" is? As you have already mentioned, what one thinks as "evil" may be thought otherwise by somebody else. With no well agreed upon definition for "evil" we cannot prove any answer to the subject of this thread to be true or false. We first need an axiomatic framework (like the math) to address such questions precisely
The next difficuly lies with "root cause". Can the human mind really know the root cause of anything at all? Let "X" be the root cause of "evil". Then what is the cause of "X"? One may say "X" did not require a "cause", it always existed... but then how do we prove it?
Ravi