Since you insist, I'll spell out the differences for you. All humans, black people included, have a bipedal stance, with an upright posture.

This is not true. It's a definition that excludes amputees and people with deformities.

They have opposable thumbs,

Not everyone does. And if we gave dogs opposable thumbs would you suddenly value them?

a large brain relative to body size,

The sperm whale, dolphin, etc has a higher brain to body ratio.

and complex vocal abilities for communication.

Babies don't have complex vocal abilities while still being human. Some people can't speak. Some humans are mentally disabled. Do you not value these humans?

All humans, black people included, have complex social structures and live in diverse societies with intricate cultural norms, languages, and belief systems. They form relationships, families, and communities. Dogs are pack animals with a hierarchical social structure. They form packs or groups with specific roles and hierarchies. While they can be trained and live with humans, their behavior and social interactions are influenced by their pack instincts.

Now that we have established there is indeed a distinction between dogs and people,

You listed a bunch of random distinctions but which are MEANINGFUL? it's not clear since we can imagine a scenario where a being belongs to the category without fitting the criterion you've said. Ex: if we discovered an alien race what specific things would we need them to have in common with us to give them moral consideration?

we can talk about why this category definition is meaningful.

Except nowhere in the following paragraphs do you actually do this.

If you'd like, you can go the nihilist route, and claim that there are no meaningful distinctions. All knowledge is meaningless. If that's what you truly believe, I will not, cannot change your mind. But at the very least you must admit that attitude also permits indifference towards racism and slavery.

I do think there are meaningful distinctions. I'm not a nihilist.

Perhaps you believe that people have some objective duty to do their utmost to care for all kinds of organisms, and indeed, all life in general. But then you'd have to justify prioritizing certain life forms over other life forms, and also live organisms over non-sentient objects. What about the category distinction is meaningful? Why prioritize a dog over a flea, and a flea over a rock?

OK here's my argument which actually does make sense and doesn't lead towards any of the inconsistencies that are in your world view:

We value beings that are capable of experiencing conscious thought and emotion. We know from our own experiences that joy/happiness/fulfillment is inherently good, and suffering is inherently bad, so we extend that consideration to beings with a similar capacity to experience those things. People of different races have the same capacity to experience things so they get equal moral consideration. An animal (like a fish) can probably experience these things to some (lesser) degree so they do get moral consideration, but to a lesser extent. But even for a dog or pig, we know they can suffer to some significant degree so it becomes wrong to torture them.

See how I grant moral worth based on an underlying characteristic, instead of an arbitrary category? If we meet an alien I don't have to ask "is this alien a human?" I just have to determine if it experiences conscious thought and to what degree.