My gf's bf just accused me of trying to steal his gf, what would you do

I am 20, and have had a gf for a while now. My gf has a friend from highschool (we go to the same school now), and we were out at a bar on saturday night with him. The bar we went to was not really a place that most of my friends would go to, so we were all just drinking on the tables. The friend's bf had not drank any alcohol the entire night and was very quiet. <br><br>Eventually, he started asking my gf questions like 'you are my gf, right?' and 'what's your relationship like with him?' and then he started to get annoyed at me. He said to me 'what's going on, are you trying to steal her?' and then he got up and walked away.<br><br>After he walked away, my gf just laughed. She did not do anything to stop him from walking away, and she did not do anything to make sure I was alright.<br><br>I have never been in this situation before, where a friend has walked away from me and said 'what's going on, are you trying to steal her?' What would you do if you were in my shoes?<br><br>tl;dr my gf's bf just accused me of trying to steal his gf, what would you do