No, Rush didn’t call her a slut. A slut does it for free; she wants us to pay for her sex, and Rush correctly identified her as a prostitute.
What Rush struggled with was: What does that make us? Johns? Pimps? Well, there is a term for someone who pays for someone else to have sex with a prostitute without having sex themselves.
The term is “idiot.”
Also known as 'best man' providing bachelor party.