Our problem with Afrin wasnt about them attacking ES areas. They cant do shit to ES areas other than a few occassional bombings. Our problem with Afrin is as long as it stays in YPG's hands there is a possibility that cantons may merge. Manbij to Tell Rifat is less than an hour in a car. And god knows what tricks US or Russia might play in the future. Not to mention thousands of hostile militants right beyond our borders. I seriously think that people who handle our mid east policies are five years old kids.