I actually think this is a really interesting argument. Here's some quick napkin math that shows a large enough difference that, I think, you can't just shut this down as a strawman:

17.7M barrels of oil annually by bitcoin mining operations

8.16B barrels of oil by US banking sector employees

These numbers don't count the physical infrastructure, servers, and other plant that these businesses own, operate, heat, keep the lights on in.

Here are my sources:

One stat I just read says that the top 20 North American banks employ 1.2 million people. That's 1.2M people eating and commuting 5 days a week for the purpose of supporting fiat.

With a quick investigation:

-US per capita annual barrels of oil: 6800 (1)

-Bitcoin annual Terrawatt hours: 30.1 (2)

-6800 * 1.2M = 8.16B barrels of oil by US banking sector employees (3)

1: https://www.statista.com/statistics/250220/ranking-of-united...

2: http://www.wired.co.uk/article/how-much-energy-does-bitcoin-...

3: http://www.kylesconverter.com/energy,-work,-and-heat/terawat...