Tariffs are protectionism, when imposed and kept in place forever. They hurt imported goods by making them more expensive. Trump is using them to get other countries (China in this case) to the negotiating table to eliminate tariffs both ways, thus making true "free trade," dropping our trade deficit with China and opening their market to our goods.
Of course, the MSM will never breathe a word of this. "Only Nixon can go to China" and all that.