Much as it often seems that the principal endeavour of Australian politics is the identification and plumping of new and juicy topics over which to brawl like a pack of cage-starved circus weasels, there is one thing — quite a big thing, really — which used to be a major fissure in Australian politics, and now just pretty much isn't. Protectionism. If you had to Google "protectionism" just now: Don't feel bad. Tariffs, protectionism and free trade — terms that nest under the national umbrella question of whether it is a good idea to protect Australian widget-makers by taxing the…