But what I dislike about seeing the xm8 in AP is due to the fact that it doesn't have a place in this world anymore, while being a good gun it had too many problems, the plastic tended to partially melt during prolonged firing, not much but stuff happened.
It feels very out of place to see the weapon in the game, and the only reason I can think of to include it is because it has a peculiar design, ie "looks cool".
To me that's what suspending my disbelief, it's hardly a reason for me not liking the game but it feels wrong to see them and I personally find them ugly.