Without getting all supportive of any ‘side’ in this, there have been times when people (some everton player, cant recall his name) have misheard what someone else has said in a foreign language (Firmino).
Seems very unlikely to be the case last night obviously, covering his mouth with his shirt shows he knew what he was saying/doing.
The fact that last nights shame is only the latest of a long line of incidents this season is another thing that makes the whole situation even more pathetic.