Godwin's Law is true, but apparently even Godwin doesn't understand why.
People inevitably make Hitler comparisons because it's the only moral bedrock we have left. There is no other issue upon which we can all be expected to agree.
Here's how Internet discussions work:
I say "X is bad". Somebody disagrees, so I say "X is bad because Y is bad". Somebody says "but Y isn't bad", so I have to say "Y is bad because Z is bad". Given the vast diversity of the Internet, there's going to be somebody who says "but Z isn't bad". To make my argument I have to find some basic moral bedrock, a thing that is so bad that we can ALL agree it's bad. Hitler is the ONLY thing that fits that description, so eventually every discussion will get there. That's why Godwin's Law is true.
Godwin's Law is about the fact that humans don't agree about morality. No more, no less.