Hoing is a tactic...not ACM.
in another age and day yes shooting someone in the back was a cowardly act....
but in the age of dogfighting...and most especially "virtual dogfighting" where 2 or more people try to use ACM to kill one another.....
well I think you know where I am going with this. 
Let's clarify something
Front-quarter and head-on (HO) are not the same thing. Shooting someone from the front-quarter is not necessarily a HO.
ACM, at its core, is established to solve weapon-solution problems, which are both angular and geometric in nature. This means that if you can get your guns on the opponent, ACM has done its job. Front-quarter shots were never in question, and absolutely
never have been.
What did come into question was the mutually-assured destruction we call a "head-on" attack, which implies zero or near-zero deflection. If both opponents approach each other with near-zero deflection, both can presumably shoot each other - this presents a danger to the pilot who wants to live past the engagement and is generally a no-brainer. The shot itself was still never in question, but rather the vulnerability it places you at. Yet again, the head-on attack
by the very fact that it has a definition is a valid ACM tactic. It just isn't a wise one to use unless you massively outgun your opponent or are at a maneuvering and airspeed disadvantage.
So, going forward -
Front-quarter shots: Good.
Head-on shots: Iffy and generally unwise.
Now that we've established that, let's focus on front-quarter shots. You seem to imply that taking a front-quarter shot is somehow less skilled... "because ACM." No, ACM exists to bring your guns onto an opponent. Whether it's done from the front or back matters not.
The real issue here is experience. When two turnfighters meet, most are usually jockeying for angular gain at the merge, which requires being offset from the opponent. This usually precludes being able to take a shot at the same time, so you rarely run into two experienced turnfighters who will take such a shot.
However, once you introduce energy fighting tactics, things change quite a bit.
Energy fighters aren't generally preoccupied with angular gains, therefore they have no inherent requirement to offset their merges, allowing them a great amount of freedom to take shots. Mix an energy fighter (who's looking for any shot possible) with a turnfighter (who is looking almost entirely for angular gains) and the turnfighter is going to get shot up on almost every possible pass. This is simply the nature of energy vs turning tactics.
An experienced turnfighter will see this and understand the dynamic of why this is occuring. An inexperienced one, or one who has little experience to anything except his style of flight, is going to make excuses and cry and whine about said tactics, not understanding why they happen or the necessity of such shots to the other style of flight.
It never occurs to the turnfighter that if they flew head-on against the energy fighter, the energy fighter would likely avoid such shots. Instead, the turn-fighter blindly continues to try to gain angles on the merge and then complains when they are shot for presenting such an undefended target to the energy-fighting attacker.
This is merging tactics 101, and is a given in air combat sims as a whole.
