Number..your friend is talking a load of excrement.
I don't know what the statistics say (if such statistics exist) but in my experience of 20 years airline flying I would say that the majority (probably about 80-90% )of airline pilots are NOT ex military .
Furthermore, military pilots are trained to fulfil different reasons for flying such as air combat and other tactical issues.
Sure, they can fly the actual aeroplanes OK, but being an airline pilot isn't just about flying the beast...it's about teamwork, commercial efficiency, and maximising safety and comfort to passengers...not all of which take priority in the military.
There's a famous saying that you can take a man out of the military, but you can't take the miltary out of a man...and all too often this can become a problem with CRM and teamwork in the flightdeck. No disrespect to the many excellent airline pilots out there who are ex - military...but don't get sucked into the myth that civilian pilots are given inferior training.
Hope this helps.
