An extreme version of this is: What should the German health service do if someone says they are willing to donate a kidney as long as it doesn’t go to a Jew?
On the one hand, nobody is forced to donate a kidney and by forbidding this we’re making things worse for an innocent patient. On the other hand, it can be seen as the state sanctioning this kind of discrimination.
Then I think you can nominate a specific person for whatever reason you want, but if it’s for racist/etc reasons you better keep it to yourself if you don’t want backlash.