I thought a HO by definition meant both planes had the shot and one plane took the opportunity. When I come around after the first merge and I have brought my nose around faster than the other guy (hence, I have a shot, he does not) I will take the shot and if I was right about the definition of the HO I am clear of all charges.

But ya know what? It's not worth the whine - if you get HOed, you didn't move out of the way quick enough and you still lost the fight. Shrug it off and re-up a new cartoon plane.
Most of the time, when someone goes for the HO on the initial merge he probably doesn't have the ability to turn on you during the second merge... Learning to dodge the HO and maneuvering against the guy on the first turn takes some practice but it's worth it in the end.