I don't know about "ethical" but justified yeah.
Certainly if media is not available for purchase I have no problem with people pirating it. But also if it's not available in a reasonably accessible format. For example, I wanted to show my son the original TMNT show. I would have happily bought it on Vudu, Amazon or Play Movies, but it's only available on iTunes. I have all Android devices and don't even have a personal Windows device, so I would need to jump through serious hoops to get it working if I bought it.