I think people find it more offensive if 1) you take credit for the work and 2) you make money by using it. But you're right, there must be some internal mental model that allows them to be so obviously different.
Yes, precisely. One case is copyright infringement for personal use, one is copyright infringement and misattribution for commercial use. Compare e.g. Bob downloading "The Dark Knight" to watch it versus Bob selling copies of "The Dark Bob, by Bob" which is actually just TDK with a different label slapped on it. I think a lot of people would find the latter to be much more wrong.
