Stealing: to take another person's property without permission or legal right

Intellectual property is property in every sense of the word.

The argument, "BUT I'm copying not taking!" is treating the property as the digital file, but that file merely represents the intellectual property.

So is the argument that the person isn't harmed because its merely a copy. First, stealing doesn't have to the mean the person suffered real harm. You can steal something I forgot I own, it won't hurt me but it is theft. But the major issue is that copyright infringement does in the aggregate hurt content creators.

Shoplifting and copyright infringement are essentially the same level of harm to businesses.