Not sure that the comment that the Woods 'Muamba' case wouldn't be prosecuted. The CPS must have decided that whatever it was,it was sufficiently offensive for it to be in the public interest to prosecute and the court decided it was worth jail.
The DPP is more concerned that every insulting or obscene remark, such as would never be considered worthy of prosecution if it were uttered in a crowd, should not occupy the courts.
The 'blow up the airport' case was ludicrous on its own facts but unfortunately was at a time when any joking remark involving a terrorist attack or the like hit a nerve.