I've seen a lot of articles on pro-cryptocurrency sites making those exact same flawed arguments. I'll break the arguments down one by one.
1. What matters isn't how much electricity cryptocurrency mining uses, it's where that electricity comes from.
This argument is based on the premise that electricity usage isn't inherently bad, because it's possible for electricity to be generated cleanly via solar, wind, or hydro power. The basis of this argument is that cryptocurrency miners could be using clean power, so they might not be hurting the environment.
Cryptocurrency miners need cheap power in order to maximize the return on their investment. That's a strong monetary incentive. But there's no monetary incentive for using environmentally friendly power, and cheap power may or may not be environmentally friendly.
For this argument to be taken seriously, it needs to be backed up by data demonstrating that miners are actually showing a preference for environmentally friendly electricity. Without numbers, it's a red herring that fails a simple logic test.
2. The banking industry uses more electricity than cryptocurrency mining.
Even if we assume this to be true (which is a stretch, because it relies on a lot of assumptions about what exactly "banking" is and how the numbers are calculated), it doesn't matter. The environmental impact of cryptocurrency mining isn't lessened by the existence of a larger environmental impact attributable to another source.
This argument is like saying "airplanes generate more CO2 than cars, therefore cars aren't hurting the environment."
3. We don't have adequate data to support the claim that cryptocurrency mining hurts the environment.
"Adequate" is a weasel word. The truth is we absolutely do have data to support the claim that cryptocurrency mining hurts the environment. Whether or not any given person considers this data adequate is subjective.