I'm sorta in the middle but closer to the purebred world. Honestly it sounds silly but I wish all the groups would get off their high horses, sit down and realize that pretty much all the groups have the same goal - improve dog's lives.
I know lots of breeders, with quality dogs, who show and compete. They love dogs and send people to rescue whenever they can, will drive for hours to help out a dog of their breed and so on. Most have nothing against a rescued dog either really, and dislike puppy millers and byb's who add to the population problem. Most have heard horror stories about AR people doing things at shows, rescues refusing to give a dog back to the breeder, suddenly increasing the 'adoption' fee for a rare breed because there isn't a lot of them in rescue and a breeder informed them what the dog was.
The rescue people I know, some are level headed, but I see a lot of death threats towards all breeders, regardless of what the breeder does. Not just 'oh those breeders' but real threats to them, their families, dogs, you name it. I've even heard a 'dog loving' rescue person say HORRID things about a purebred pup that walked in the door with his ears cropped - I get that it's an issue with some but really?
It would be really cool if breeders and rescues worked together. Imagine if rescue litters got temperament tested by an experienced breeder, who then helped figure out which pup went to which owner, and then was on call to help those puppy owners. Or the foster home whelping the litter and raising it with that experienced help. Lots of breeders drive dog friendly vehicles to get a breeding done, pick up a dog, go to dog shows, imagine the transportation help there. Or the 'do not adopt' lists. Or if someone really wanted a purebred whippet and didn't care if it was from a rescue or a breeder, and either group worked together to find that person a dog either way.
Add to that here, the HS is in the middle in a lot of ways. They will work with the rescues, and yes, do 'kill' some animals when required to do so. If the dog isn't adoptable, if it's not a dog they'd want their neighbor to get and have next door, or is likely to eat another dog or a kid, then no, it's not put up for adoption and put down. The rescues in the area BASH them quite a bit for being a 'kill' shelter, but at the same time, if it's a dog they aren't likely to adopt out, or that needs a lot of work, they're full, take it to the HS. I've even heard that the rescues have dropped their dogs off but it's not official because that's the HS's policy.
Pot meet kettle.
The HS has a lot of funding, a vet clinic, a building and staff.....
And round and round. Funny thing is I know people on all three sides and they all still love dogs, mixed or not.