The UN resolution didn't say anything about policing hate speech. It said countries should work against racism. If you think it's not the responsibility of a government to ensure that racism and fascism don't take root under it's watch and lead to catastrophies like what happened in Germany, Cambodia, north korea, china, Uganda and currently in myanmar then I dont know what is seriously wrong with you
And yes you can and should police hate speech if such speech leads to violence or terrorism. It doesn't even have to be a criminal matter but something easily addressable in civil court similar to libel laws.