I misunderstood what you meant, but this argument still seems specious.
The people currently employed by the financial industry would not cease to exist if the financial industry did not need as many employees, they would find jobs elsewhere. The downstream effects of what people spend their wages on isn't part of the the actual impact of the industry they work for.
Yes, they would find jobs elsewhere, and their energy consumption and pollution would no longer go to support the finance industry. If you want to make a fair equilibrium comparison, compare the current state of affairs with a future state of affairs where the population is smaller by the amount of people who currently work for payment processors.
I'm on the fence about whether this is correct or not. The question in my mind is: do you include military spending in the cost of maintaining a fiat currency and if so to what extent?
Fiat currencies are backed in part by the power of the governments that issue them, so is defense spending a form of "proof of work" for them? If the US government disbanded its military would the USD hold any value for very long? Same goes for any other fiat... e.g. if the PRC disbanded the Chinese military would the Yuan retain much value?
If fiat currencies require a constant demonstration of credible military (and police) capability, that's a rather enormous cost and brings with it quite a bit of resource use and pollution.
(I would guesstimate that Bitcoin would still be less efficient than USD but that the margin would be smaller.)
We're talking about the relative efficiency of Bitcoin vs. conventional finance in an energy or other cost per transaction sense. I'm asking whether some amount of military spending should be counted in the cost of maintaining a fiat monetary system.
If people were using Bitcoin as currency directly its value would remain equal to whatever people were willing to trade for it. Obviously if all people were willing to trade it for was USD it would become worthless, but that's not the point in this thread.
Bitcoin has other problems as a currency but that's not the topic of discussion here. Some other cryptocurrencies try to solve these, such as it being too deflationary or lacking functionality.