SC
I haven't seen another XF on the road in the UK yet, so I can't comment on how the others actually drive or behave.
I haven't had any problems with a 350z or the odd M3 or TT, but you get the berk in a Vectra or Mondeo who wants to race. I just let them get on with it. Once they have zoomed off, I can speed up and follow at a safe distance, knowing that they will need to brake if they spot a police car. My own early warning system...
I don't feel like I have to prove anything - there are faster cars than the XF and if I'd wanted a different car I would have bought one. My XF makes me feel great whether I'm going slowly or at speed.
Good luck with your anger management courses.