He did provide a source; it was implied. He is thinking of Doctor von Münchhausen's Famous Field Fact Finding, where two DJs were sent walking through a park in the company of dogs; one with an unleashed Pitbull Terrier, and the other with a leashed Labrador Retriever. The one with the leashed Labrador had much more success approaching the ladies, which shows us that:
1) dogs are great convo starters
2) women love bondage (cufflinks, chains, leashes etc)
Obviously then, calling a woman a dog who should be chained is the ultimate neg hit.