"This is political policing," it continued.
"This is a carnival of distraction.
"14,000 babies are about to die of starvation in Gaza, with food sent by the world sitting on the other side of a wall, and once again the British establishment is focused on us."
Officers from the Met's counter terrorism command were made aware on 22 April of an online video from the event.
Belfast man Mr Ó hAnnaidh has been charged under the name Liam O'Hanna.
An investigation was carried out, which led to the Crown Prosecution Service authorising the charge.
Earlier this month, the Met said it would investigate online videos allegedly showing the group calling for the death of British MPs and shouting "up Hamas, up Hezbollah".
Both Hamas and Hezbollah are banned in the UK and it is a crime to express support for them.
Hezbollah is a Shia Muslim political and military group in Lebanon which has been involved in a series of violent conflicts.
Kneecap say they have never supported Hamas or Hezbollah and would not incite violence against any individual. They say the video in question has been taken out of context.
A number of gigs featuring the band have been called off since the videos emerged.
They are currently scheduled to headline Wide Awake festival in Brockwell Park, south London, on Friday.