His closing the border between us and China was a correct action but it was still racist.
It was racist because he used the virus to further poke at China and add to his push of a new cold war instead of any legitimate reason regarding slowing down the spread of the virus.
It was racist because he uses the terms “kung-flu” and “the China virus” to further 'other' China towards this goal of a Cold War. Everyone knows you have to demonize and dehumanize an enemy to gain and maintain support war. Problem here is that the racist tropes apply to all Asians, including Japanese, Cambodian, Vietnamese, Koreans, South Pacific Islanders, etc., many of whom are now living within our borders and are in fact American citizens. Regardless of where they came from, they are now our brothers and sisters and should be cherished as such. This 'othering’ of our Asian community is just as wrong as 'krauthead' to demonize German immigrants during WWI and the internment camps of Japanese Americans during WWII. It cannot be allowed to stand.
If the action of border closing was simply an action of virus response, he would have closed the border completely to all nations, at least temporarily, to buy us more time to get a handle on the community spread already happening within our borders. He would have locked down the Washington town and that California town (sorry, can’t remember now where exactly those cases were) and gone in “guns a’blazin” to contact trace and quarantine anyone who has become sick and anyone they’d been in contact with.
Doing so would have prevented the need to shut down the whole country. But he didn’t do that. Because his reason for closing the border to China had absolutely nothing to do with the virus.
You don’t get points for half measures that come nowhere close to solving the problem when everybody knows you acted for other reasons and goals to start off with.
Hence the criticism.