Stopping someone from mocking Islamic teachings

Q: There is a person on the internet, who seems to be a Muslim yet makes fun of people about things which are a part of Islam (e.g. The ruling on eyebrows, he thinks that these things aren't a part of Islam). Is it permissible to use harsh words to stop this guy.

A: Yes.

And Allah Ta'ala (الله تعالى) knows best.

Answered by:

Mufti Ebrahim Salejee (Isipingo Beach)