A simpler example: Today you buy $100 of Theranos and $100 of Uber. Tomorrow your Theranos is worth $0 and Uber is worth $200. You put in $200, you still have $200, you use the Theranos loss to offset the Uber win. This is good, this is how things should work.

But some here would say "OMG he evaded taxes on the $100 Uber gain!"

Tax loss harvesting is not a loophole, it's exactly the right thing to have, and it's available to everyone.