Of course he was being sarcastic. Nonetheless there were dummies claiming that the Parliament Hill shooting was staged by the government to provide justification for anti-terrorism laws.
Cybercoma, the term "false flag" refers to an act carried out in such a way that the act is assumed to have been performed by someone else. Historically there was a naval tactic by which a ship would fly different colors to get close to an enemy vessel, then strike their colors and fly their real colors when they were in range to engage (see the movie "Master and Commander" for a fictional example of this being done.)
Later and more deceptively it has been used as a pretext for war. For example, the Red Army went to the border with Finland and shelled a Russian border village, then claimed the Finns had done it and declared war against Finland... thus creating a completely fake justification for the Winter War (in which they got whipped. Karma.)
More recently and more on-point is the idea of committing acts of terrorism as a pretext for staging war against a presumed sponsor of terrorism. Operation Northwoods was a never-implemented but real plan concocted by the US government which CIA spooks would commit acts of terror against the US and blame it on Cuba, giving the US a justification to invade Cuba.
And this is what the conspiracy people are talking about, particularly in regard to 9/11. If the US government had a plan to commit fake terrorism to give them a justification to invade Cuba, then maybe 9/11 was also a plan invented to provide pretext to go to war.
And the same people are convinced that the mass murder at Sandy Hook elementary school was a fictional event created by the US government to create an excuse for gun control laws. And so on. Any time anything bad happens, anywhere, the same kooks are out there shouting that it was a "false flag operation" created by the government to give the government an excuse to do something. "...take away our guns!" "...take away our Confederate flags!" In this new world, nothing ever happens on its own, it's always part of a larger secret agenda run by the government, Jews, Illuminati, or 12 foot tall shape-shifting lizards from space.
-k