Fatwaa from Shaikh AbdulAziz Bin Abdullah Bin Bazz (Rahimahullah)  From his book 'Islamic Fatwas regarding Women' Page #259

Question: What is the ruling concerning one who ridicules those who wear the proper hijab and cover their faces and hands?

Response: Whoever ridicules a Muslim woman or man for sticking to and applying the teachings of Islam is a disbeliever. This is regardless of whether it is concerning woman's hijab or any other matter of the Shariah. This is based on the following narration from ibn Umar: At a gathering during the Battle of Tabuk, one man said, "I have not seen anyone like our Quranic readers who is more desirous of food, more lying in speech and more cowardly when meeting the enemy." A man said, "You have lied and you are a liar. I shall definitely tell the Messenger of Allah (Sallallaahu Álayhi Wasallam) about that." That news was conveyed to the Messenger of Allah and the Quran was revealed. Abdullah ibn Umar added, "I saw the man holding on to the bag of the camel of the Messenger of Allah and the dust was striking him while he was saying, 'O Messenger of Allah, we were just joking and playing. The Messenger of Allah (Sallallaahu Álayhi Wasallam) was simply saying the verse of the Quran],
"Was it Allah, and His Signs and His Messenger you were mocking? Make no excuse, you have disbelieved after you had believed. If We pardon some of you, We will punish others among you because they were sinners" (al-Tauba 65-66).  So ridiculing believers has been equated with ridiculing Allah, His Signs and His Messenger.