>"Why do people act confused when I say that socialism is theft?"
Because socialism is the negation of capitalism, which is a system based on theft. The bourgeoisie steal wealth from the proletariat through extraction of surplus value. The mass hoarding of wealth caused by this would lead to the immediate implosion of capitalism, if it wasn't for the state stepping in and redistributing the wealth--that is, re-stealing the wealth back from the bourgeoisie--and giving some of it back to the proletariat.
>"What happens to form a society that stops using currency"
You mean what happens when resources stop being allocated based on profits and instead become allocated based on human need? When the production process is based upon human need rather than profits?
How exactly is this "theft"?
>"no longer has personal property rights"
Socialists and communists are explicitly in favor of personal property rights. What we criticize is private property rights.
Personal property is commodities that you own that can be utilized by you personally. e.g., the shirt on your back, a personal computer, your family photo album, etc.
Private property is the personal ownership of the means of production. The means of production are that which is used to produce commodities. Factories, farms, office buildings, etc. No single person can utilize these things. It requires hundreds of people to operate a single factory. The concept of "personal" ownership of these things is nonsensical.
Not only is it nonsensical, but it directly leads to theft, as the workers--the proletariat--do not own the means of production in which they work on, so the owner--the bourgeoisie--gets full control over the fruits of their labor. Naturally, the bourgeoisie keep most of the wealth produced by the workers for themselves, paying the workers only a small fraction of the wealth they produced.
You have to work or else you will starve. Work is inherently coercive, and the worker cannot simply buy his own means of production, the worker cannot simply buy a factory or farmland, or an office building or what have you. The worker is therefore forced--coerced--into working on someone else's private property.
Due to this, they lose the right to the fruit of their labor, and have a large chunk of it--the "surplus value"--stolen from them by the bourgeoisie, who do none of the labor themselves.
These days, the bourgeoisie typically don't just own a single factory or farmland or whatever. They own shares in corporations. Each shareholder gets a vote on the board of directors in the corporation, the board of directors being the people who run the corporation, including the CEO.
The proletariat is therefore coerced into working on someone else's property, where they do not own the fruits of their own labor, where the rulers of that property--the board of directors--are elected, not by the workers, but by oligarchs they have never met before.
Of course, those oligarchs don't work in the corporation, they have never met the workers, they do not care about them in the slightest. So they vote for a board of directors that will steal as much wealth from the workers as possible
The goal of a socialist society is to abolish the bourgeoisie by having the workers control their workplaces themselves. The proletariat would elect their own board of directors. They would all have a say in how their own workplace is ran.
>"and the state controls every business?"
The state is an apparatus of class oppression. Every class-based society in history has been a pyramid, where the lowest class has the most amount of people, and the highest class has the least.
Under feudalism, there were more peasants than knights, and more knights than royalty.
Under capitalism, the proletariat is the majority of the population, while the bourgeoisie is the vast minority.
Maintaining a pyramid of oppression is rather tricky, as the most oppress classes have the most people in them, and thus the most power, and could overthrow the entire system at any point.
Capitalism arose when the bourgeoisie--the middle class of feudal society--overthrew the aristocracy at the top, and became the new rulers of society. In order to maintain these class hierarchies, you need a state, which has the purpose of oppressing the lower classes of society and maintaining order.
Capitalism is the dictatorship of the bourgeoisie. The ruling class of society are the property owners, who hoard massive wealth, and use that wealth to control the state and the media. The bourgeoisie are a minority of the population, but have control over the majority.
A socialist society would overthrow its bourgeoisie and replace the dictatorship of the bourgeoisie with the dictatorship of the proletariat. That is, the state would be ran by the workers--the vast majority of people. The bourgeoisie would become the oppressed class.
All class-based societies throughout history are pyramids. Socialist societies are upside-down pyramids. The majority is the upper class, the minority is the lower class. The bourgeoisie lose their power, and remain oppressed by the state, until they cease fighting and join the majority as proletariat.
Once the bourgeoisie are done away with, there will be no more classes. The proletariat--the workers who control the entire government--will be the only ones left.
In a society with just a single class--and thus the abolishment of class antagonisms--the state itself will fade away. This is when you reach communism, which is the goal of a socialist society.
That is to say, the goal of socialism is to abolish the state. Not to maintain it.
And even under socialist societies, the "state" doesn't own everything. The state is just a tool of class oppression. Most property in the USSR, for example, was owned collectively. Collective property refers to an arrangement where those who work the property own it equally and democratically. Collective farms were not owned by the state, but by the farmers who actually worked on the farm.