MP who fights for minimum and living wage laws advertises for an intern? Of course she's a hypocrite, but the moral justification for minimum wage laws is on shaky ground to start off with.
What about charities? What about doing a friend a favour? What about doing your own housekeeping? You're working for yourself for free. Just because it's you doesn't mean that there hasn't been unpaid labour involved, where someone else could have been paid to do that work for you for a wage. How are any of these things really different to hiring an intern?