When it is reasonable to tell a parent you don't agree with their parenting?

[Noneofmybeeswax]

I always thought someone else's child was their business but just recently I have concerns about a child's welfare. I won't go into the ins and outs but long story short the 1 year old child is regularly left unattended in a car for extended periods (30 mins or more). The parent is rarely more than 100 yards away but out of eye sight and ear shot. When the parent returns the kid is often crying.
WWYD? Keep your nose out? Say something to the parent? Report it?

This is child neglect, for a young child it would be very scary to be left for that long. I did use to leave DD1 (now 9) in her car seat between the ages of 18 months and 3 years old when she fell asleep in the car at nap time, as I just couldn't transfer her without her waking up, and she used to be a nightmare in the evening if she didn't have enough of a nap. I was constantly checking on her, though, and obviously the windows were open.

It wasn't ideal, obviously. With DD2 (now 6), I could transfer her into her buggy and she would go on sleeping for another hour sometimes.

In the case described by the OP, I would report. It wouldn't be an isolated incident, I'm certain.

The reason the 'horsey' thing is relevant is that horsey mums might be needing to have child somewhere safe, whilst they bring in/turn out/ride in the school.

So not relevant then in the same way as if I a non horsey Mum fancied leaving DD in the car while I went for a swim for 30 mins it would also be an awful thing to do.

It's not ideal parenting, though I have yet to meet a perfect parent.
Please don't judge unti you've walking a mile their shoes.

Yeah, I don't believe you have to keep your horse when your baby is on the way. If the horse isn't saleable give it away. Or pay someone to take care of it. It's really dangerous to leave your baby for half hour chunks of the day, every day. Different from in a cot with a monitor.

If the horse is a good enough excuse why isn't shopping or going for lunch with a friend?