Why flip me off?

06WRXsti

So I was up in portland OR to see a trail blazers game. I drive a 2006 wrx sti as my daily driver and on the way back I ran into a few wrx's and a we were "racing" around on I-5 and a yellow 370z pulls up. I get all excited because I actually own a restored 1972 240z and am working on a 260z. So we race around a bit. He beats me by about 3 car lengths and a little farther down we run into some traffic and we are almost completely stopped and I roll down my window to tell the guy nice car and that I have a 240z and he rolls down his window flips me off and says F YOU. and pulls off at the next exit..... I was like...... oooooook. Just felt like venting.