OK now first of all do you really think in Halo 2 bungie would take the time to show point defence guns firing out side the SMAC lvls? No because it would be a whast to ad that in out side there just worried a bout making the lvl inside that your play fun and interesting. And the books why would they say "oh just FYI SMACS have point defence" it would be irrelevent. All modern naval ships have point defence that can shoot every thing from jets to missiles out of the sky, and halo is how many years in the future? And plus if point defences were shooting at boarding craft in halo 1 and 2 then the first missions in those games would have been lame, so bungie not going to worry about them in the game. But logical weapon design says they would need to be there.
Ok this is getting old, I've allready countered the whole "Why would they say something irrelevent" arguement. Going off your arguement, of why would they go "SMAC's have point defenses!" in the books, answer me this, why did they bother going "Halcyons, frigates, destroyers, and Marathons have point defenses!". Knowing that ships have point defenses is irrelevent to all plots in the books, but they say it anyways.
I mean hell, they go so far as to specify exactly how many point defense guns a ship has, and even what caliber round they fire! So obviously the books have NO problem giving out "irrelevent" details, so if they're willing to go to such depth with ships, why not the SMAC platforms?
As for your game comment, why bother making the MAC gun fire during the outside portion of the SMAC level? It's irrelevent, and adds nothing to the level except detail. Oh yeah, detail, THAT's why they'd add point defense guns. To immerse the player more. That's why they added archer missile pods and point defense guns to the frigate in Halo 3. And hell, they mighta been on the frigate in Halo 2, we just didn't have the chance to see em.
So all in all, stop making up retarded excuses. The end fact is, NOWHERE does a canon source state a SMAC has point defense guns, and as illogical as it is, and as much as you'd all like to think they do, they don't. And this mod strives for realism, and so the SMAC's ingame shouldn't have point defense either.
P.S. I think Spectre got it right, I only know of two planets with SMAC's, Reach and Earth. So if the planet is important enough to have SMAC's, it has a full time defense fleet that can act as point defense and anti-fighter screen, why bother building point defense guns on the SMAC, and keep it supplied, when the fleet surrounding it can deal with fighters?
P.S.S. Here's an idea, for all of you who aren't content with the way this is, email Bungie and ask them if SMAC's have point defense guns. They're usually pretty good about answering emails, surprisingly enough, so get a response and that'll be that. Cuz Untill I hear official word about this, I'll go off what I've seen. Which is absolutely nothing.