> people generally are arguing past each other in regards to the single definition they're thinking of.
It's more than that. By claiming that copyright infringement isn't stealing, they're usually doing so to justify such behavior: if the original thing remains with the owner, it couldn't have harmed him, could it?
Maybe but I try to give people the benefit of the doubt, especially when the argument at face value is factually incorrect.
By conflating unauthorized copying with stealing, they're usually doing so to justify excessive punishment. If the owner lost what they had, they were obviously harmed, right?