He probably used the word faggot as an insult, not necessarily implying that anyone is gay. My friends and I would call each other faggot in this way back in high school, even though we are all straight, to express displeasure and to convey all of the insult that the term holds for a straight person. 

 That’s not really actually how slurs work. While you might joke around with your straight friends about it, it’s in fact the homophobia in the term which gives it the edge that makes it an insult to your straight friends.