Eh; I get it. Was it professional? No. Was it worth getting under your skin? Also no.
I dump buckets daily and it is a CHORE. It’s one of those little things in life that seems like no big deal, until you’re dumping multiple buckets day in and day out. When the bucket is full of foul smelling poop water, it just adds to pile if you’re already irritated or trying to get to your next item on the to do list. On the occasions I find them, I also bleach the buckets which means not only am I dumping - but I’m going to get the bleach and a scrub brush and my task that was supposed to take twenty seconds is now taking several minutes. Not a big deal if you own one horse, super irritating if you are managing twenty (kind of like the blanketing debate).
If it was the only water the horse had - totally unacceptable. But if the horse was being turned out and wasn’t even using the stall - not worth a second thought. They should’ve dumped it when they found it, but maybe they were running to their next appointment.
The “your horse is a pig” comment was probably pent up frustration. I have a couple who are filthy pigs and I try to leave them out as much as possible. It’s no one’s FAULT, but dealing with one of my perfect angels who poops neatly in one corner vs one of my heathens who somehow breaks all manure into pieces too tiny to pick and scatters them throughout the stall… night and day. Add manure water to the stall casserole and there are days you just want to walk away.
Not a barn owner, but I own my own facility and have eleven personal horses (because I’m nuts) so I’m going to count it.