P-51D might be easy for a GOOD PILOT to get kills in because once it has it's speed, it maintains it fairly well (If kept coordinated and the pilot has an idea what he is doing). However, it it's hopelessly outmatched by a lot of the LW plane-set once it loses said speed and requires an "experienced" P-51 pilot to actually compete. Generally good pilots know this, so they BnZ, which allows a build-up of kills from a rather safe distance. Most new pilots have NO IDEA about E retention, coordination, and how to lead a target, and when they fly the P-51D, they mostly end up dead.
The propaganda argument is absolutely silly; the propaganda doesn't keep people from calling it a dweeb ride. In fact, the propaganda is the reason we see huge amounts of whines that the P-51 isn't "uber enough" in this game. They reason that if it actually "won the war," why does everything outmatch it?
Spit 16's, LA-7's, (insert "dweeb ride" here) are the planes that outmatch most in-game aircraft in multiple dimensions.
Try to fly a P-51D like a Spit 16, and you will quickly realize why it actually does take some skill to dogfight a P-51. Fly a Spit 16 like a P-51D and you'll get the same, if not better results. The Spit 16 is one of the most forgiving aircraft on the planet, in terms of stall, E retention, power-to-weight, maneuverability, and just general engage/disengage ability. This is also why it is the most recommended aircraft to new players.
When you really look at the stats on the birds, you'll find that the P-51D is actually a very mediocre fighter. It's only big advantage in terms of real-life: It's range.
When it comes to the Brewster whines... It's because people misjudge it's E state. "WHAT?! HOW did that Brewster keep up with me at 500mph?!" "I'm pretty sure it's because he dove from 15,000 feet... but who knows." "Not possible. Nope, it's overmodeled."
