The thing is, you can never re-evaluate your position on anything if you assume people actually agree with you but feel obliged to voice disagreement for arbitrary reasons.
Take this discussion for an example. You think tactical marksmanship and related poses are ******* awesome. I respect that. In fact, I kinda agree. Taking cover, presenting a smaller target and holding a gun in a way that facilitates fast aiming are the things that help you survive a firefight, and in the end, a guy walking away from the battlefield is more awesome than the coolest looking corpse.
But there are many brands and flavors of awesomeness, and I sincerely don't think this one fits the Space Marines in any way. Their awesomeness stems from the fact that they transcend the need for such behavior.
Consider this as a comparison. Let's say you have a kung fu master. He can strike awesome poses, punch through a wooden wall and jump so high he might as well be flying. Then, you have a telekinetic, who stands seemingly disinterested, can punch through a wooden wall with his mind, and actually can fly.
Which image is cooler? That's a subjective matter. But which image projects more power? One guy can kill you with a fist, the other can kill you without even lifting a finger. It's pretty obvious who's more powerful of the two.
In the galaxy of warriors, the Space Marines are the equivalent of the psychic guy. They don't position themselves to present a smaller target, because they are immune to small arms fire anyway. They don't position themselves to stabilize their weapon, because it's perfectly stable in their augmented, power armor-clad hands. They don't look down the sights, because between their perfect muscle memory, millions of bolts shot during decades of daily drills, and their mind and body directly interfacing with advanced targeting systems of their armor, they can fire from the hip with perfect accuracy. Ultimately, they don't do any of that because every second spent positioning yourself and raising your weapon to look down the sights is a second you're not killing your enemies. That's right - all the things normal warriors do to survive and win in a firefight are nothing more than a waste of time when you're a Space Marine.
I find that context is crucial in determining whether something is cool or not. A bazooka is an awesome weapon - it can take out a vehicle or a flyer, or it can take out an entire nest of opposition with one good shot. But if you use it to shoot a single guy standing out in the open, suddenly it's not cool - you've just wasted a precious rocket on something you could have done much more easily with a single shot from a side weapon.
I feel the same way about Astartes and tactical marksmanship. It's wasteful, indulgent and doesn't serve any purpose. These are two great flavors that don't taste great together.