Do you think food/treat aggression/pushiness is something to work on?
Absolutely. Just like every other instance of 'bad manners', with a horse sized beast, it can become dangerous, not just annoying & 'rude'. Therefore I insist on teaching/enforcing 'good manners' be it with food or otherwise, 'treats' or 'meals'. And part of that is that if I go into a paddock with horses, they aren't allowed to play 'horsey politics' with eachother while I'm there either.
Can treat aggression/pushiness be "fixed?" If so, why try to fix food aggression/pushiness, but not treat aggression/pushiness? I've heard it is because horses need food, but don't really need treats. Technically speaking, under what circumstance is it absolutely vital that they mess with the horse while eating?
So... I'm not exactly sure what you're getting at. Again, regardless whether it's meals/hay, or treats, be that given for training or 'just because', or Bad behaviour when there's no food involved, I think teaching & reinforcing 'manners' around people is vital.
Yeah, it's not 'vital' that you 'mess with' horses while they're eating... unless you include dishing out the feed in the first place, of which I'm absolutely going to 'mess with' them if they're rude about that, and they won't be getting their meal while they're behaving in a manner that's unacceptable. I don't allow 'rudeness' at any time & I'm not about to allow it in one situation but not another - that would be inconsistent & unclear to the horse. **On that note, if a horse is going to be handled/fed by others who may not be consistent with what they reinforce(like 70yo fathers...), then it will make it more difficult to teach the horse to be 'polite' with other people.
I hear it so often, that people blame food treats for 'pushy' or 'nippy' or 'aggressive' behaviour. This only shows that those people just don't understand training principles. In essence, boiled down, horses learn to do what works - what they get reinforced for, and they quit doing what doesn't work for them. Therefore IF you reward 'bad' behaviours, that's what you'll get more of. If you NEVER reward 'bad' and you do reward 'good manners' then you will get more of the good and the bad will stop happening.
In short, it's not food(treats or otherwise) that causes Bad behaviour, it is what behaviours are being reinforced.