Yes, they do exist and according to what I found on the internet, they have been persecuted and oppressed for centuries... This is what Wiki says about them for example:

"Since the spread of Islam began with the early Muslim conquests of the 7th–8th centuries, Yazidis have faced persecution by Arabs and later by Turks, as their religious practices have commonly been charged with heresy by Muslim clerics. Most recently, the 2014 Yazidi genocide that was carried out by the Islamic State saw over 5,000 Yazidis killed and thousands of Yazidi women and girls forced into sexual slavery, as well as the flight of more than 500,000 Yazidi refugees."

I don´t want to play down the incident that you described in the post but if I compare the facts and numbers here, your interpretation sounds severely biased...