The barking is in response to his supposed "Internet girlfriend", /u/SportyStrawberry, hinting that boys wearing dog collars sexually aroused her.  This post is a response to the age old adage "The pot calling the kettle black."  I.e. Ricky posting a picture of a man in no better shape than he.  You can read more about the saga of /u/PeaceLoveAndRamen here https://voat.co/v/ProtectBerry/comments/871341