I do, because the domain being displayed isn't the domain that my browser has contacted. Whether or not the content is guaranteed to be unchanged isn't relevant to this.
I don't think that's terribly analogous. The difference is that when you're using a CDN, the traffic is being redirected on the server side, behind the domain name resolution.
That means that when I go to a site that is using a CDN, my browser isn't lying to me about the domain I'm contacting. It is correctly reporting that information. Whatever routing happens behind that domain is a different issue.
I do, because the domain being displayed isn't the domain that my browser has contacted. Whether or not the content is guaranteed to be unchanged isn't relevant to this.
It reduces my ability to trust my browser.