Oooops, my bad... Time index 1:20, don't look like M249 to me (background) In any case just because the M249 was used for full auto suppressive fire, doesn't mean that an M4 would have been useless in that particular instance. Just the existence of M249's means that full auto is here to stay
Edit: If the president of Armalite considers full auto a necessary feature in the modern battlefields, I'd sincerely doubt he's talking out of his rectum
I agree that full auto is less useful in the terrain and conditions that they have in Afghanistan, but even then, it has its uses. In an urban setting, where a good chunk of small arms combat will be happening and even in dense foliage, you can't deny the usefulness of full auto, especially if your projectiles can reliably penetrate light cover like car doors and foliage.
http://kitup.military.com/2011/01/video-lack-of-full-auto-on-m4s-cost-lives.html