For all you who aimed to integrated Facebook contacts and are now believing that it was a mistake, here's how you can get rid of Facebook Contacts from coming up on your iPhone/iPad contacts lists.
How Do I Delete Contacts From Facebook
Perhaps you have actually set up your Facebook account in iOS, while not understanding that a contact sync would occupy your address book with lots of entries that may be unwanted. Fortunately, this option is completely reversible.
Go to your "Settings" app and pick the "Facebook" entry, then disable the toggle labeled "Contacts". This will get rid of all Facebook contacts from your locally stored address book. The contacts/friends themselves will stay active on Facebook, so don't worry.
If you open the "Contacts app" on your iPhone, you should see that of the entries previously noted in the "All Facebook" group are totally gone now.
The best ways to hide Facebook contacts on iPhone.
If you wish to keep the additional contacts that are synced from your Facebook account to your iPhone's address book (" Contacts" app), but hide them from the main contact list, you can do so by adjusting your view settings.
Open the "Contacts" app and tap "Groups" at the top left of the screen. Then scroll down to "All Facebook" at the very bottom and uncheck the item on the list. You can check other group to make it noticeable, such as your iCloud contacts or other groups you might have enabled on your iPhone. Tap "Done" when ready.
The "Contacts" app will now hide the Facebook contacts in the primary list view. Your other contacts ought to still be visible.
Tip: You can handle contact groups straight on your iPhone. Find out more How Do I Delete Contacts From Facebook.