Which is unfortunate, because government involvement in business is a socialist idea, not a capitalist one.

Who enforces capitalist property rights?

Upholding the rule of law (punishing fraud, theft, murder, and other infringements of the rights of others) is the job of the government in a free market system. Protecting consumers from themselves and picking businesses to subsidize/grant privileges to is not.

The gray area, which I consider to fall in the 'upholding the rule of law' category, are consumption-based regulations or incentives, where a practical piece of society (like burning fuel) infringes on the rights of many others to a small degree, and this is where a carbon tax could easily fit in a free market system. In fact, it could be argued that the system is freer than if there were no pollution taxes at all, because then people would be allowed to infringe on the property rights of others (via shared atmosphere, oceans, climate) unhindered.

Historically property rights were defended by the owner.

Unless you mean before written history then no. Governments have been mediating property disputes at least as far as the written word and likely though the last 100,000+ years.

Do you believe that when we all lived in huts that the feudal lord would send out knights to defend you if your neighbor decided to take your property?

Under a medieval feudal system, most people did not own property the way we think of it today; the feudal lord did. If the lord wanted to take all your clothes and throw you off their land, they could, with impunity.

That said, yes, the feudal lord's band of merry thugs would keep the peace, because peasants can work harder if they're not squabbling with each other.

>Under a medieval feudal system

You don't have to go that far back in time:

https://en.wikipedia.org/wiki/Patroon

It's not that clear cut. If a poor person gets robbed today the cops will do basically nothing. Feudal lords will defend vs Viking raids. So, they both sit betweeen 0 and 100% on this.

In feudalistic society there were hundreds of small "governments" in a society, all of which had to defend their own rights.

You're making the exact same mistake they are.