I’m not sure that this has a factual answer but I’ll start it here.
Dogs are fairly universally loved and valued by society big calling someone a dog is supposedly insulting. I believe that it is even more insulting in Muslim cultures. Is there a reasonable or logical reason for it? Calling someone a cat would be confusing and AFAICT, is not done in English speaking countries.
It’s somewhat similar to calling somebody a child. Children themselves are generally highly regarded. But an adult who is equated to a child is being seen as less than a full adult.
This goes way back. dogs were not companions back then but workers/slaves of their masters.
Like the Quran the Bible doesn’t have great things to say about dogs, and have used the dog as a unworthy human:
Rev 22:14 “Blessed are those who wash their robes, that they may have the right to the tree of life and may go through the gates into the city.15 Outside are the dogs , those who practice magic arts, the sexually immoral, the murderers, the idolaters and everyone who loves and practices falsehood.
(Or just dogs just can’t get into heaven by design)
More famous is the story of the Caanite woman who rebuked Jesus (and won) in Matt 15:
26 He (Jesus) replied, “It is not right to take the children’s bread and toss it to the dogs.”
27 “Yes it is, Lord,” she said. “Even the dogs eat the crumbs that fall from their master’s table.”
Also while dog is not mentioned by name, In the book of Ruth of the Bible, Ruth starts out a very low member of society, and has a very dog like action sleeping at the feet of the land owner Boaz.
I would have thought that anyone who has owned a dog, other than a pampered pooch, will know that dogs are amoral, lazy, uncaring of personal hygiene and have disgusting ideas about what is good to eat.
Cats don’t get off scot-free. “Catty comments” are deliberately hurtful and/or spiteful remarks.
George Carlin on dogs:
"Dog is lying out there in the living room, you got all these people sitting around, you got a little chip, a little dip. Dog’s in full view of everyone, got carrot sticks, celery sticks, little lady fingers, finger ladies, all sorts of little things that you got. And everybody’s eating nicely, and you look down and you realize that the dog is licking his balls. No one says anything, no one mentions it, spectacular thing going on. Hey, if I could reach, I’d never leave the house. "
Calling someone a “dog” is basically saying that they’re unable or unwilling to control their “base” appetites. Dogs don’t really do temperance. They’ll eat 'til they get sick, then eat the sick. They’ll fuck under absolutely any circumstance, regardless if it’s appropriate at that time, or with that person. And while famously loyal, their loyalty is indiscriminate, and not based on the worth or station of their master - a dog will be just as devoted a servant to an itinerate drunkard as they are to a reigning monarch.
So, basically, calling someone a dog is saying that they lack temperance and propriety, and that their nature is essentially subservient.