The fact you can download it with this tool is because the artist is letting you listen to it for free before buying it. Downloading it with this tool seems totally unnecessary and a bit of a jerk move. Bandcamp hosts mostly small and independent artists and labels.
And from personal experience I can say, sometimes people want or have to consume media offline, because of unreliable or slow network or expensive providers. But this doesn't mean that they won't pay later if they like it.
Personally, I consider it immoral to pirate Windows without a very good reason (which doesn't include "I like using Windows", or "I want to play game X" or "I want to use the enterprise version which doesn't have baked-in ads").
The same moral principles that argue against depriving people of natural property they already own do not imply further arguments against reducing sales opportunities for non-rival goods for which scarcity has been artificially established via positive law. Other, unrelated principles, can make for compelling arguments, but not the same ones.