A valid HO? I'm upping from a base on the coast where the fighter hangers have been wacked and there is an enemy CV 15 miles out - I up an a20 with 8 x 500lb bombs and try to do what I can to save the base.
I get up to about 5K when I spy a Seafire and an F4F coming at me head on - the Seafire is only 3.0K out, so I set course for him and he obliges by coming right at me. At 800 I open up with my .50s and saw his wing off while I take a couple of 20mm hits and my left engine starts losing oil.
The F4F, seeing this, does the smart thing and peels left to swing around and get on my tail. At this point, I'm just entering CV ack, and knowing it is more important to get my bombs out on target than it is to try to start a turnfight with an F4F, I outdive him to target, level at 1000 ft and start dropping bombs. The CV ack dutifully blows me to shreds, but I do get a couple of hits and take out a load of guns.
Am I guilty of an HO - yup. I don't feel bad about it a little bit here, because my objective is to get bombs on the CV, and that objective is accomplished. The tactic itself isn't the problem, its just when and how it is used that people should take more into consideration.
If I'm in an LA7 (God forbid), and my mission is air superiority, I'm likely to be doing some B&Z through a furball somewhere. Should I HO there - probably not unless I absolutely have to, because 1 ping in my engine or a pilot wound and my mission is over. Better to B&Z down from the rear quarter and give someone a 20mm enema, pull back up and wait for my next opportunity. I can HO and probably get a kill (maybe while being killed), or I can be smart and have a shot to get multiple kills, and maybe even land them.
There are times you want to take the Head On shot - if you are in a ride that is just plain outclassed by the opposition (say 110 on a Spit), if you are new to the game and not that confident you'll get another chance, or maybe even if you are wounded, leaking oil, gas or otherwise certain you aren't going to be in the air much longer anyway. In those cases, go ahead - take the shot, if I'm giving you the opportunity, it's my fault if I get blown away by it.
The situation should dictate the tactics - if your tactics are only HO passes, then you are limiting yourself and failing to learn. In the end, that is bad for you and good for me - you'll get some kills, but I'm more likely to accomplish my objectives.
EagleDNY
(An unrepentant base porker who will HO you to accomplish his evil plans for world domination - be warned)

$.02