In fact, if you watch the video, the officer is explaining, quite clearly, this part from "General Rules for the Use of Parliament Hill" (last updated in 2018, clearly pre-dating the recent unpleasantness):
Why, yes, waving a massive flag that reads "Fuck Trudeau" (even if "Fuck" is spelled with a maple leaf) pretty obviously runs afoul of general rules prohibiting what you can read in the last sentence above.
So if Ezra Levant could, you know, shut the hell up and stop lying about shit, that'd be great, thanks.
P.S. Read the non-negotiable regulations for the legal use of Parliament Hill, and start making a list of how many were broken by the FluTruxKlan idjits. Seriously, make a list. The rest of us will wait right here.