When a Mormon male 15 is asked if he believes in love at first sight and responds with do you believe all is fair in love and war what does he mean?

This boy's religion has nothing to do with his answer. The fact is, he is a 15 year old boy, and most teenage boys arent thinking about love. He probably didn't really know how to answer because he hasn't thought of love at first sight, and that was the first thing he came up with.

However, because he is a Mormon, he probably will not date until he is 16, and may not be okay with having a serious girlfriend until he is 18 or even 20 (when he comes home from his mission). So even if he does like you, he probably won't do anything about it.