"As in taking something and depriving the owner of it. Copyright violation is not theft, copyright violation is copyright violation."
Copyright is the right to determine who can legally own a copy of something... It's kinda right there in the name. Copyright, in the U.S., is a property right, and property rights are defensible in court, even if the property in question is not physically removed (e.g., trespass).
Further, appropriating the fruits of someone else's labor without their consent constitutes "theft of services", or doesn't the U.K. have that one?