To some degree, it's a moral stance. I tend to see mining as hoovering up hundreds, thousands, maybe tens of thousands of GPUs, all in the name of jumping on a pyramid scheme, get-rich-quick bandwagon. Even worse, it's doing that while the *real* profits are going to the guy who 'created' that particular cryptocurrency. And I still can't work out why you need cryptocurrency for legal transactions. Does it have a purpose other than buying things you can't legally buy and blackmailing people? It's digital cash, and it has all the anonymity and lack of security that goes with.
That, and I really hate the idea that someone gets to take a GPU away from someone who wanted it for it's original purpose (gaming), run it for a year, then sell it on to the gamer with wear on it. It is scalping under another guise, only instead of doubling the price of the product and immediately re-selling, the miner extracts that value over time and re-sells at purchase price.
Buying from a scalper guarantees more scalpers will arise because the business model keeps working. If you don't like scalpers, you have to not buy from scalpers.