I basically agree with this. The other issue is, why is it not OK to discriminate based on race and ethnicity but OK to discriminate based on, say, gender, sexual orientation or gender identity or socioeconomic class?
If a party holds that all women, all transgenders, all bisexuals, or all working-class people need to be deported to concentration camps, then banning it would be a good idea as well.
If we keep on expanding the definition of "unacceptable speech" beyond the "race and ethnicity" criteria DFB mentioned, we enter increasingly subjective territory of what is and isn't "unacceptable".