The argument is exactly on points that one cannot dis/prove in a duel. The 190D9 is a very poor plane to duel with. However, in the MA it consistently tops the list of unperked planes in its stats. In special events and scenarios it rules and does much better than the 109K. Climb is not very useful in large scale engagements that are not at tree tops level, but is very valuable in a duel. In such situations, dive and speed (and never-exceed speed) are much more important defensively than sustained turn rates. Visibility out of the cockpit becomes exponentially more important as the number of planes in your vicinity increase. Ammo load and ease of aiming becomes more important in large scale engagements where you cannot ride someones 6 for long till you get the perfect shot. The ability to take damage and fight on. These factors are non-issues in a duel.
1v1 fights are the litmus test of tactics. The MA is simply application of those tactics against a wider range of targets. To claim that climb is not very useful in large engagements is to assume that you'll never end up at the edge of a furball with a slower, lesser-climbing opponent behind you - it's a very misguided assumption. Every tactic employed in large-scale combat is built upon a corresponding component of 1v1 tactics. If 1v1 tactics did not work in large fights, no pilot could ever score a kill by themselves.
If everyone flew to survive above all else, we'd find that the fights in the MA would utilize the majority of the same tactics we see in the DA. The difference is that the MA's mentality is generally "kill kill kill!" while the DA mentality is surviving ("win win win!"). There is a focus in the DA to survive; it just so happens that the way to survive is to kill your opponent quickly with the least loss of position and/or energy. Ergo, 1v1 tactics rely on selecting the most efficient maneuver (response) to a given situation.
MA flying, on the other hand, covers up individual deficiencies. If a pilot makes a mistake in the MA, they can disengage and run to cover... and we see this as perfectly acceptable (although annoying). However, what we neglect to address is that the pilot diving to the deck is running to friendly assets, whether it's wingmen or ack. If you consider that ack or wingmen isn't available to the opponent, we begin to realize the ridiculousness of the argument. It becomes apparent that the "it only works in the MA" argument is really just an admission that the tactics do not really work in and of themselves, instead requiring outside variables to be successful.
This is why any tactic considered effective to a single pilot in the MA must also have merit in the DA. Otherwise, it's not a tactic, it's simply poor flying that's compensated for by rolling with large masses of friendly pilots.