Whoever makes fun of a Muslim man or woman for adhering to the Islamic sharee’ah is a kaafir, whether he is mocking a Muslim woman for observing correct Islamic hijaab or for some other reason. ‘Abd-Allaah ibn ‘Umar (may Allaah be pleased with them both) narrated that during the campaign of Tabook a man said: “I have never seen anything like these Qur’aan readers of ours. They have the biggest bellies, the most lying tongues and they are the most cowardly when meeting the enemy.” Another man said, “You are lying, and you are a hypocrite. I will most certainly tell the Messenger of Allaah (peace and blessings of Allaah be upon him) [what you have said].” He told the Messenger of Allaah (peace and blessings of Allaah be upon him), then Qur’aan was revealed. ‘Abd-Allaah ibn ‘Umar said: “I saw him (that man) hanging onto the saddle of the she-camel of the Messenger of Allaah, (peace and blessings of Allaah be upon him), stumbling over the stones, and he [the Prophet (peace and blessings of Allaah be upon him)] was saying,
“Was it at Allaah, and His Ayaat (proofs, evidences, verses, lessons, signs, revelations, etc.) and His Messenger that you were mocking?”
Make no excuse; you disbelieved after you had believed. If We pardon some of you, We will punish others amongst you because they were Mujrimoon (disbelievers, polytheists, sinners, criminals)”
[al-Tawbah 9:65-66 – interpretation of the meaning]
So mocking the believers is equivalent to mocking Allaah, His verses and His Messenger. And Allaah is the Source of strength.