No matter how well or bad you place smoke on whichever side, it will almost always help the offense.
Sure the MGer might be blocking enemy reinforcements, but that lane may be vital for your own troops to get into a cap zone, and smoke may be better.
I'd guess my mentality to the game is like this. We all glorify the MGer who blocks an area, or the sniper who seriously weakens the enemy suppressive fire, or the commander who just called arty that took out 5 people. However, the game is won by people that just get in the cap zone. Usually, they accomplish nothing else besides getting in the cap zone. A good amount of them are riflemen who cannot really do much in the often close quarters of the cap zone, or they are afraid of dieing so they just hide, etc. Sometimes you see an smger kill a bunch of people in a cap zone, or a rifleman stab a bunch, but for the most part they just get in and stay in as much as possible.
They are the guys that win the game. They need as many bodies that come as possible. Smoke is a multiplier effect, as is just having the commander in the cap zone. Everything else is secondary. The commander thus has to worry about effectively doing two multiplier effects which are *huge*. He also has to call arty (which imo is less important than smoke but more so than MGs) and keep himself alive in the cap zone. He really does not have time to worry about the MG, if he does he is doing something wrong. He should always be *way to busy* unless he is on defense.
If he is on defense and using smoke, he is doing something wrong 99% of the time.