"When the ignorant address them, they say salām." (25:63) Good people don't answer, they say ‘salām’. There is no need to argue with an ignorant person because he has fixed ideas and don’t want to understand. Now there are many of them. In non Muslim countries they may be dangerous. The best answer to an ignorant is to keep silent. Just keep quiet and be happy and Allāh ﷻ will reward you.