Funny horse behaviour

Question
Hi Rick,
I wondered if you had ever seen something like this before. I am the girl with the 9 yr old mare and the 13 yr old gelding. You have helped me with many questions in the past so here comes another one:
My mare and gelding are stalled at night, but they have very large runs with see-through fencing so they are not locked up and are able to socialize. They are next to each other and are pretty good buddies. We had them out on pasture Sunday and just took the day to observe their behaviour. The pasture is next to our friends gelding's stall & run(who is the "lead" gelding) and our gelding approached him. There is a fence (see through) between them so they couldn't get at each other, but it wasn't pretty. Pinned ears, a little bit a nipping and THEN, my mare got between them! It was like she was breaking up the scuffle. Both our gelding and our friend's gelding like my mare,,, :-) But here's the weird part: When we put the two of them back in their stalls, my mare gave our gelding HELL! She was flaring her nostrils, bobbing and shaking her head at him, pawed the ground next to the fence and then turned around, aimed and pooped right in his face. Do you think she was pissed at him???? He just kinda stood there with his head submissive and wondered what just happened. Will a mare scold by bobbing her head? I know the pooping thing can't be a good sign,,, (HA! HA!) I tell ya,,,the more I learn from my horse the smarter I get. It looked like he clearly did something that made her mad.

Answer
I have said this a 1000 times, horses locked up alone next to another horse is not good, they are not happy to see another horse, they do not have horse friends next to them, that is all bad and makes a horse protective, makes a horse aggressive, it makes a horse develop negative behaviors, yet I constantly get emails telling how lucky a horse is  to have a horse in the next stall or in the next pasture.  IT IS NOT THE SAME AND NOT GOOD FOR THE HORSE.

As for what is going on, people often tell what they see and if I watch  the same thing I see something totally different.  Normal for horse geldings to want and compete over a mare, maybe the other geldings impressed her more, maybe he pushed away and not she respects him more, maybe she saw her gelding back down and give to pressure and now she does not respect him and thinks he is lower and now she will push him around.

Horses don't hold grudges and don't pre-plan things, they act in response to actions and other acts, you saw what she did and probably did not see what caused her to do it so you assumed it was a grudge or she was thinking and holding on to something from earlier.  People do this, not horses.