Often when people are offered alternative views, when they feel they’re in the wrong, it just makes them sadly more entrenched in their own positions.
This is why I don't argue like this anymore - unless I just can't help myself, and it does slip out from habit sometimes

As soon as you argue against something someone is doing, you put them on the defensive and they become more entrenched - and even start to believe more strongly - in their original viewpoint. That doesn't help anyone, including your own stress levels. (I've posted this before but it's always worth a read:
You're not going to believe what I'm about to tell you - The Oatmeal)
If I feel like I have to say something, then phrasing it as "When I was in this situation, I did this.... I felt like this..." means that you can get your own point across, without giving them anything to argue with. Even if you - er - stretch the facts sometimes.
"I know, it's so difficult when you have to work, but when I was in the exact same position with my latest pup, I just felt that it wasn't right for a puppy to be alone for that long without any interaction, so what I did was...". It won't always work, of course, and we just can't expect people to change their views in an instant, but it might cause a little flicker of recognition that starts to grow. And especially when you're in that sort of environment where insinuating that what they're doing means that you're also saying that many of the other people are doing it wrong - they're bound to also jump on the defensive and it turns into a shit-show of division.
I totally understand the reason all of us want to grab these people by the collars and shout at them, and I admire the way you kept your cool, Mags, but the reaction from those others just screams defensiveness. Once those barriers are up, you're not changing anyone's mind, however polite you are about it.
I'd walk away from the stress of that group and find yourself places where you're happier. Facebook is full of wonderful groups of wonderful, likeminded people - you just have to filter through the reams of groups filled with troglodytes to get there
