Tariffs will not protect jobs. Employers are concerned about maximising profits, not maximising jobs. There is no control over profits, to make sure they are used to maintain or increase employment. Increases in profits are used to fund new technology, which can be used to replace workers. BHP in Newcastle was given government subsidies and improved productivity by workers, but it still decided to shut down the plant.
Unions joining with bosses is harmful to workers in a number of ways.
Instead of leading workers in the fight against employers for better wages and working conditions, unions blame foreign countries and foreign workers. Protection of industries in an advanced industrial country like Australia adds to the exploitation of Third World nations and to the super-exploitation of Third World workers. Protectionism in the developed countries stifles industries in poor countries and increases their burden. Bosses benefited from the racism they fanned by paying immigrants low wages and using them as scabs. The same logic led worker to massacre worker in the first world war.