This never-ending argument about the effect of difficulty on price is really hard to deal with, you are right about the human nature part and that IMO is the only way for the difficulty to have an impact on price, have a look at this chart



This is the hash ribbon indicator, one of the most (if not the most) accurate indicator in Bitcoin history, the way the indicator works is by analyzing miners' capitulation, and since miners are large players in econmical system of bitcoin, their capitulation means something to the price, so if you believe that most bull rallies start when people give up " buy when there is blood in the streets" then the difficulty drops which are essentially hashrate drops should be of meaning to you.

Now I also doubt that price goes up or down with difficulty just because of a random event, but huge drops or spikes in difficulty could indicate high levels of fear/greed and to me, those are great opportunities to buy/sell if used alongside other price analysis.