To be honest, I didn't think Gerrard should have been charged, nor do I think Lennon should.
The rule (below) relates to the accusation of bias or incompetence. By the letter of the law, Lennon should be charged as he clearly indicates incompetence. However, if a ref has had a shocker (never seen there game, don't know if that was that case) then you should be able to call them out.
No recognised football body, club, official, Team Official or other member of Team Staff, player or other person under the jurisdiction of the Scottish FA, reported to the Scottish FA by a referee for misconduct, or any such body or person, shall, in an interview, a “blog” on the Internet, on a social networking or micro-blogging site, or in any other manner calculated or likely to lead to publicity which is brought to the Scottish FA’s attention or of which the Scottish FA becomes aware by whatever manner or means, criticise the performance(s) of any or all match official(s) in such a way as to indicate bias or incompetence on the part of such match official or make remarks about such match official which impinge upon his character.