Neither have I ever claimed he said it is always harmful. My claim is exactly the same thing you are saying now. He claims to have a definitive answer to the question of whether harm is the most common result or not. His answer is that it is indeed the most common result.

I don't think you've been reading the correct question. Take a look at it one last time:

"My claim is that I do not know whether harm is the exception or the rule. The person here claiming to have a definitive answer to that question is you, not me."

If it makes it easier, that can be rephrased as:

"My claim is that I don't know whether harm occurs most of the time or not. The person here claiming to know is you"

That's a different way of saying the exact same thing I said before.