Your opinion is welcome and I definitely see your point. IMO however, the infantryman could use the extra punch and range that the M14/SOCOM II would provide. Correct me if I'm wrong, but an M25 or standard M14 with optics would be considered a sniper rifle, and not a DM rifle.
Granted volume of fire would be affected.... but then you have to look at the structure of a fireteam or squad, as well as the kick of the weapon.
Recoil -- having fired both many times, I would say that the M1A can be fired reasonably quickly with a trained shooter compared to the M-16. Is the -16 going to throw more downrange, ofcourse yes, but again that goes to the philosophy of 5 well placed rounds, as opposed to 15 not so well placed rounds.
Fireteam/Squad structure - your SAW gunners and -240 gunners are going to worry about volume of fire IMO. But even in that aspect, the M14 series could probably fire 7 or 8 rounds to every 10 fired by an M-16... not much of a difference in volume of fire.
SOC isn't the only group requesting these weapons... and from what I've heard they're seeing use with regular infantry too. Availability and contracting issues I would say play a part in the use of the weapon... infantrymen that have used it (I have a friend in the 82nd) are pleased with its all around performance.
You made good points though... many of which are standard and I've heard on more than a few documentaries. However, you didn't speak to one KEY issue -- Reliability
The M1 garand is the grandad of the SOCOM II. It was built with a sturdy and durable design, with a completely different receiver grouping. The weapon has proven to jam much less, and require less cleaning (although naturally your infantrymen are going to clean it anyway). This is why many Marines complained about the M-16 in Vietnam... they were used to a reliable weapon that wouldn't jam and could be carried through mud etc. and still get up and fight.
Last but not least... the standard infantrymen could use the penetration of this weapon to great effect. Using volume of fire against a fortification, or brick wall for example... an infantry squad firing all 7.62 is going to take those structures apart (or go through them). Theres also the obvious uses against vehicles, hardened or not.
Again... good debate, good points. Matter of preference. I'm sticking to my guns on this one (pun intended).