I personally suspect that the creators of Life of Brian were hipper than they let on. If you look at the videos of the protests that occurred in different cities, the signs were identical. Now, that could be a coincidence, or the protesters could have organized themselves across all those different jurisdictions and co-ordinated the signage, or distributed the same signs to the different groups in different cities.
But I also know that protest-for-hire is a thing, and that the Entertainment Industry is in business to make money.
"You can't have a better press agent than a censor. " - John Waters