Is it permitted for a Muslim to kill the enemies of Islam, like Christian missionaries, or like those who put a ban on headscarf, or those who attack Islam verbally?
Allah the Almighty commands in the Quran;
“Allah does not forbid you from being kind and equitable to those who do not fight you because of religion and do not expel you from your homes. Indeed, Allah loves those who are equitable. Allah only forbids you from making friends of those who fight you because of religion or expel you from your homes or aid in your expulsion. The ones that make friends of them are the wrongdoers.” (Al-Mumtahanah/ The Examined One 60:8-9)
According to the verses, people who cross these three red lines are the only ones to be fought against. That is to say; either they fight us because of religion or expel us from our homes or aid in our expulsion. No Non-Muslim can be killed apart of these reasons. Cases in your question are related to the following verse:
“You will surely be put to test from your properties and lives. And you will surely hear from those who were given the Scripture before you and from those who associate others with Allah much abuse. But if you be patient and guard yourselves; indeed, that is of the matters of determination.” (Al-e-Imran/ Family of Imran 3:186)
No other way is advised but being patient, cautious and determined against those who offense and speak agonizing words.
Please click on the link below for detailed information on relations with Non-Muslims: