> The conno­ta­tion of dis­cern is one of per­cep­tive recog­ni­tion of non-obvi­ous under­lying truth; the conno­ta­tion of dis­crim­inate (since the 1860s) is quite the opposite, being more of an unjust impo­si­tion of differ­ence where none is deserved.

(emphasis mine)

The key here is that discrimination is imposing different treatment of people "where none is deserved." When a pandemic is happening, you're not imposing "different" (and unjust) treatment upon foreign visitors - you're imposing necessary treatment as a precaution to help reduce the spread of the virus. This is a good thing that we want to do, not an unjust thing.