The trade war with China is probably the only thing in which I agree with the Trump administration.
There is no free trade with China, China still has very strong protectionist policies. Access to the Chinese market is very difficult, as a company you have to produce your goods in China to sell them there and often times you have to cooperate with a chinese company to gain market access. The Chinese state also owns 51% of all factories in the country which means every foreign company who produces in china gives the chinese state full control over their facilities, hand in hand with that goes Industrial espionage which the chinese are known for. Knowledge is the most important resource in today's information age so western countries who are especially dependent on knowledge have to do something about china's behavior.
So you see, trading with china is not fair at all. It's debatable if Trump uses the right measures but it's good that the US finally does something about it.