a particular system of values and principles of conduct, especially one held by a specified person or society.
Now if your moral system has enslaving folk as ok, then fine, but if you're a person with consistency, or any historical knowledge about what slavery does to a slave-using area (technological stagnation), then you should be opposed to it.
You're playing with words here. You say that forcing people to do anything they don't want to do is slavery, and then argue that slavery leads to technological stagnation.
First of all, I don't think slavery always leads to technological stagnation. The Great Wall of China was built with 1 000 000 slaves, for instance. Secondly, paying taxes is not the same thing as being forced to work and having all your human rights taken away (which are upheld by the evil state btw), even if you decide to call them both slavery.
So if slavery is forcing me to do anything I don't want, and you are trying to force me to live in a stateless society, then you are enslaving me. That's immoral!