Monbiot is, apparently, British slang for Moonbat.
According to the article the incident took place at a literary festival in England where Bolton was invited to speak:
"Mr Monbiot was blocked by two heavily-built security guards at the end of the one-and-a-half hour appearance, before he could serve a "charge sheet" on him.
"After being released by the guards the columnist - a fierce critic of the 2003 American-led invasion - made a dash through the rain-soaked tented village in a failed attempt to catch up with Mr Bolton."
Reminds me of rat chasing an lion. What would he do if he caught it?