> If gold and silver aren't treated "like kind", and facebook and google stocks aren't treated "like kind", why would bitcoin and ethereum be treated like kind?
For the same reason that, say, transferring your wealth from an Irish bank account to a German bank account doesn’t trigger a capital-gains event in the US?
I.e., those other things you listed exist “within” the US financial system. Cryptocurrencies exist outside of it, similar to the way assets held in other countries do. If one of these countries had multiple active currencies (say, the GBP and the Euro in the UK), a US citizen telling their UK proxy-holder to start moving money from one into the other has nothing to do with US financial regulation, only UK financial regulation. It just so happens that moving money from one cryptocurrency to another has to do only with the financial regulation of the country known as “the Internet”—which has no capital-gains regulations.
(Of course, things are slightly different if the management company exists as a US corporation—in either case. Ask yourself what a US company offering GBP+Euro management would do in this case. The answer should be obvious.)