Why is it that when the YPG (Sunni Muslim Kurds) are guarding the christian areas in Syria, the christians become a target?

Al Masdar News reports: “On Sunday evening, a female suicide bomber detonated an explosive belt in front of the St. George Syriac Orthodox Church in the city of Ras Al-‘Ayn, killing and wounding several civilians in the process. According to local activists, the woman was reportedly a displaced Syrian from the provincial capital of the Al-Raqqa Governorate – her identity was not revealed. Ras Al-‘Ayn is currently under the control of the predominately Kurdish “People’s Protection Units” (YPG) and their political wing “Democratic Union Party” (PYD); this city has been the target of several attacks by the Islamic State of Iraq and Al-Sham (ISIS) and Turkish Army.”

https://www.almasdarnews.com/article/female-suicide-bomber-attacks-church-northern-syria/ | Al-Masdar News