There is no debate. Copyright infringement is not theft. Copyright infringement is also not murder, arson, or vandalism. Words mean something. That's why we have different words for different things. When someone says "Copyright infringement is theft", they're making a rhetorical point by conflating two different things, just like when someone says "All property is theft." This does not mean there is any debate that "property" and "theft" are the same thing.