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The small stubby little M4 has the rep for having an edge over the M16 in close fire fights?

Might have something to do with the 10ish inches you can potentially save between the collapsible stock and shortened barrel - which also makes the gun, comaratively to the M16, a dream to tote around all day or squeeze into whatever vehicle you've mounted.

This smells to me, because our Marines use the M16 as their main battle rifle, and they have the rep of being top dog fighters...

Amongst ignorant civilians and mall ninjas such as yourself who buy the hype presented in TV shows and commercials.

So why do the Marines use the longer 20 inch barrel? It helps the 5.56 maintain that critical velocity so it can work its magic and cause hyper static shock to the target and massive tissue damage on the cellular level.

Probably has to do with an irrational hatred of carbines actually. And I think you mean hydrostatic shock, but whatever.

Must be why the Marines are such top dog fighters. They use the right weapon for the job of killing people.

That must be why organizations that use carbine length weapons like 75th Ranger Reg, CAG (Delta) and US Army Special Forces, US Army Airborne, US Army Air Assault, Navy SEALs etc are so second rate compared to the Marines.

They say the M4 is close and acceptable, but it does not have the edge over the M16 in fire fights.

Which you base on nothing.

I have a bias because the M4 was invented for Arabs, and was never the original design of our battle rifle.

Which isn't factually correct and even shorter variants were common in SOCOM since Vietnam.