Ailz's dad used to do it all the time. It usually meant he had some unspeakably obnoxious opinion to impart. Ok, he was a decent enough bloke but his opinions were grim- and the pointing made them grimmer.
And today, on the front page of my Mother's newspaper, is a photo of Boris Johnson pointing across the aisle of the House of Commons- presumably at Jeremy Corbyn. Oh, the cooked up drama! The aggression! What a bad example it sets to the youth of the nation!