The jibe was found on Chris McCann's social network site the day after Nicola Hughes and Fiona Bone were killed in Manchester in September 2012.
It read: "F*** your GMP (Greater Manchester Police) only 2 of yous (sic) should have been 22 of yous."
McCann, 30, a father of two from the Gorbals, once reported to be a leader of a notorious city gang, was charged after police were alerted.
It led to him appearing at Glasgow Sheriff Court, where he pleaded guilty to breaching the peace.
Sheriff Ian Miller deferred sentence, but told McCann: "Custody is very much in my mind."