Was I out of line, when I told a flirtatious Mexican waiter, "Eres Coqueto!"?

I was with an american group (all of us college kids) (myself a Spanish speaker, once-lived-in-Mexico American girl) at a Mexican restaurant, this past week. I spoke with the waiter in Spanish, and he was getting flirty. He then switched to English, and asked in front of the guys at my table, which of the guys were my boyfriend. I got embarrased (seeing as I have a crush on one of them) and then in Spanish, said, "Eres Coqueto!". He countered with, "porque", at which point I blushed, looked down, and he left. Everyone at my table said, "What did you tell him?????" I was like, "I called him a flirt!" They thought it was mean, too direct, and hurtful. Was I out of line, given the Mexican culture, and how flirty and bold Mexican men can be?
Note: I LOVE Mexicans, though..