Do you have heat in your house? If so, you're literally wasting a ton of electricity. At least bitcoin miners and folding@home folks are doing something besides productive along with making heat.
There's a few games similar to WoW but with harsher death penalties like losing equipment. This equipment can also be stolen through various cons or whatever. It's against the terms of service, but this gear or the money can be valued in $ as people do trade for it like that.
Should stealing someone's enchanted chain armor +6 defense result in someone going to prison? What makes bitcoin different?
You claim that lower taxes makes inequality, but think about the poor people who would be locked out of owning a car if the taxes went up to some arbitrary amount - they literally wouldn't be able to get to certain jobs.
Heating your house using a normal furnace is wasteful when you could be securing bitcoin or folding@home for science research, but we ignore this huge energy cost so there's really no reason to rant about bitcoin.
Luckily there's at least a few businesses and such experimenting on putting miners and servers etc in people's houses and running them hard all winter.