Ok, this is not a flame, just a simple question...
TC got angry with me last night because he said I ho'd him.  My take was he was in a Pony D, higher and faster than me.  I was in a Jug N, and low and slow.  We made a not quite direct HO pass, and I dinged his engine and made him smoke.  
When I first started playing, I wouldn't pull the trigger on the HO because a lot of folks said it was bad form.  After being HO'd by just about everyone, I started fighting fire with fire.  To be honest, if I'd known it was TC, I wouldn't have pulled the trigger, because I know he wouldn't do it to me.  But, I'm gunshy at this point because I've been shot down in HO when I didn't pull the trigger, and the other guy did.  Now, I pretty much expect it, so its a reflex.
So, my question is this--is there a time--any time, when the HO is not considered bad form.  If I'm defensive in a lessor plane, being dove on by a better plane that has alt and speed, is it still bad to HO in an attempt to drive them off?  Does the other guy automatically get rewarded for his e-state by deserving a clean approach to my six?  If a Hurri II, Il-2, 110, C-Hog, etc. pull into me for a HO pass, I'll pull off to avoid facing those guns.  I have been flying the jug a lot, and if I'm on the deck slow, I don't feel like I have many options...
If there's some technique I don't know, I'd be more than happy to learn.