The law doesn't even say it's okay. What FaceDeer is referring to is that copyright infringement is a different category of crime than theft, which is defined as pertaining to physical property. It's a meaningless point because, as you said, this isn't a courtroom and we aren't lawyers and the concept of intellectual property theft is well understood.
It's a thing engineers and lawyers often seem to do, to take the way terms are used in a particular professional jargon and assume that that usage is "the real" usage.