IME banks consistently see DCC as NOT a matter of principle. In the few times when I complained, the banks always just credited me the claimed overcharge without opening a dispute.
I also learned an interesting factoid during a recent trip to Chile, where DCC was pervasive. Most payment terminals were programmed to only work one way, Vendors would even let me do the input, and the option without the DCC would simply get declined. Eventually I resigned myself to this "involuntary tip" of about a $1 USD. At their low prices, it was still a great deal to shop there.