Why is it people that play call of duty think they know everything about guns?

So like I'm just wandering because I'm at the shooting range with one of my friends and I had a Barrett with me ( it is NOT a fifty cal) I'm not sure what round it took though it was my dads and he paid for ammo and the targets and lane and my friend just starts talking about guns like he knew everything when everything he was saying was false an I asked where he learned his information and he said call of duty and I would pass by a lot of other people at school and such about this same situation it's confusing to me haha sorry for all the long typing