It's obvious to everyone, even the Jocks, that that pic of Cathy is going to get the DIKs in trouble but it doesn't mean that they did it. Dawe is just taunting them with a well-known fact and Tommy is both stupid and angry enough to believe that his snide comment means they did it.
I mean let's be honest, the Jocks are nowhere near smart enough to pull off something like that. Leon even said at the party that Anthony tried clicking on one of Camila's posts twice thinking it counted as two likes.