slavery in the Monster Manual

I found a copy of the original AD&D Monster Manual, and was reading through it.

Giant beavers: Standard Intelligence, and you can trade with them. You can also sell their young on the market for certain prices.

Blink dogs: Standard intelligence, Lawful Good. You can sell their young etc.

Giant Eagles: Standard intelligence, friendly with elves and dwarves, and you can sell their young etc.

Dragons: Low to High Intelligence, can be subdued, and sold on the market.

Also, Nixies. Neutral alignment, yet they like taking slaves via charm magic. They let you go after a year, I guess that makes it okay????