Tariffs are price increases on products sold in the US. For every middle class family that purchases items at Walmart or other discount stores it is likely those lower prices are a result of the products being manufactured overseas where costs are lower. A tariff raises those prices hurting the consumer, the retaliatory tariffs on US goods, especially agriculture hurts US farmers.
The policy is not a good one, it creates instability in the economy and if it continues will most likely lead to a recession in the final years of the Trump Presidency. The President is living in the past, he doesn't listen to actual economists and depends on his outdated, uninformed opinion about macro economics.
Being a businessman does not qualify you to understand macroeconomics. The two are not equivalent, anymore than the best physical therapist isn't qualified as a orthopedic surgeon. Related fields does not mean equal knowledge.