Here we find the crux of the confusion. A copyright is not a property right of the sort one has over a physical object. It is, rather, a monopoly created by an affirmative act of the state. While the rights created by copyright law are as worthy of protection as other rights, there are critical points of difference which must be kept in mind.
But it doesn't mean they're obligated to give you what you want, or to let you infringe their rights just so you can watch it the way you want
Er, we are talking about someone watching a DVD he owns using a computer he owns. The people who sold the DVD exchanged all their rights concerning that copy for whatever cash was handed over -- there is nothing to infringe (provided that additional copies are not created and distributed, of course).
Successfully viewing the contents of a plastic disc on X, Y or Z operating system is not some God-given right of yours.
Success in any endeavor is never guaranteed. The right to pursue any endeavor, absent a showing that it entails a violation of others' rights, is guaranteed in a free society.
But they're in no way immoral for protecting their property.
Again, what they have is not "property", but a government monopoly on the duplication and distribution of certain information, and even this is not violated by the viewing of a lawfully obtained DVD on a lawfully obtained computer.
But the very purpose of copyright is to provide intellectual property with protection that's akin to that of a "physical object." If creativity literally plopped out of our brains in little nuggets we could hold in our hands, there would have been no need for the state to define and codify it. So for the purposes of discussing copyright, it's certainly OK to call intellectual property "property." That's what it is under law, no matter how we got there.
I've acknowledged the distinction between the DVD encryption situation and other copyright issues. Sorry I crammed it all together and muddled the basic point I was trying to make. When it comes down to it, yes, I certainly have the right to do whatever I want with the actual round piece of plastic I've bought -- put it in my cat's food dish, try to make it play on my operating system, whatever.
The contents of that disc, of course, remain the property of someone else (the copyright owner). But it sounds like we already agree that it is wrong to use decryption to distribute unlicensed copies of a work.