Homophobia?

Wall of text incoming: Hey, so I have two friends - friend A and friend B - who know I'm gay, and when I told them, they were both completely fine with it. Yay! But, one day, during school (we're all aged 15-16) I was sat next to them, we were all on computers, and A goes to the toilet. B then goes onto A's computer and tampered with A's work for a joke. What did he type on the computer? 'Gay fag'. I know this wasn't directed at me, but man oh man it hurt. When A got back, they both laughed about it, me staying silent and looking away awkwardly.Then, earlier today, we were in a similar situation: all on computers, A walks away, B types something. This time, 'Person A likes men'. Intended as an insult.So here's my predicament: I have two friends who know I'm gay and accept me - but they both have made jokes that, in my eyes, are homophobic. I talked to person A about the first time it happened, but he just shrugged it off and said it was just a joke. What should I do? When this happens, I get really sad and feel more alone, it's really getting me down!Oh, and they both knew that I'm gay before the first incident.Thanks in advance.