I don't agree. The only circumstance where difficulty would have no influence on price is one where someone could pay for the expense of mining with bitcoin. This is most likely not the case, and miners must sell the btc they mine to pay for things like electricity, which would reflect the downward pressure on BTC price. However, with a decrease in difficulty, miners are effectively producing more at the same expense, which may alleviate some of that selling pressure. How much, I'm not sure.
Miners don't produce more. The production of coins is independent of difficulty. It will always be 3600 coins a day (until 2017 or so). Satoshi produced 7200 coins a day with his PC (before the last halving).
What you are saying is that miners, at high difficulty, will have a different saving/spending attitude for bitcoins (that is, they will only convert what they need to cover their costs) than when the difficulty is lower. In as much as miners are hodling, that may play somewhat, yes.
In as much as miners systematically convert into fiat, and take their profit in fiat, there is no effect either.