I hate it when people redefine "stealing."
If you have a nugget of iron, and I take it from you without your consent, that's stealing.
If you have a nugget of iron and are offering it for sale for 10.0 BTC, and I find an equivalent nugget of iron and offer it for sale for 5.0 BTC, and now nobody will pay you 10.0 BTC for your nugget, but will only pay you 5.0 BTC, I haven't "stolen" anything from you, even though you have suffered a loss of value.
Just because somebody's actions result in a loss of value for your assets, that does not mean anybody has "stolen" anything. Every day, people outcompete other people and the value of specific assets decline. That is not stealing. If I buy a bunch of stuff at certain times and sell a bunch of stuff at certain times, and it affects the market value of your stuff, that doesn't mean I'm a thief!
You're playing with the words here. You perfectly describe a healthy market (unregulated and manipulation free market). And with this condition (fair market practice), you're totally right about "stealing" word is non-sense at all. However if you add bad guys (manipulators with fiat) to any healthy market, the word "stealing" becomes available to these operations. Have you ever heard JPM's paper short selling on silver (AG)? It is called manipulation by all means. How can you short more than total world silver? (I mean total world silver as un-mined and mined silver together) With paper selling (short one) via futures market it is possible. In this way you can control everything and its prices. Don't believe me, it is just another conspiracy theory. Yeah,,, just google it!