I find Wikipedia a useful jumping off point in general to get a sense of common criticisms on a variety of topics. In this case, I'd start in the Reception section of Sowell's:
Are you referring to Economics in One Lesson? It looks like that's Henry Hazlitt, not Sowell. (Am I missing something?) It looks like DeLong has some criticism of that.
Just to be clear, I'm not an expert on any of this. I just popped in to provide a pointer I've found useful in learning about a topic when I'm not sure where to start. Similarly here, I just applied a bit of search-fu.
An interesting idea is that mine, unlike that defined in the link, is defined by force of the individual first and foremost. My dogs and cats all have a sense of mine. They own things. They keep things from one another to the point of force if necessary. Mine is that which I hold by force. For the modern society, the force is, at least for the most part, yielded to the State. Indiana or Florida enforce mine. I promontory not kill those who seek to take from me in exchange for the State using its collective force against my adversaries.
Property rights and violence, the two dont go without each other in any fundamental discussion.
The standard view here is that the state is the guarantor of those rights via a monopoly of violence granted by the people.
The libertarian view is that the state didn't ever contractually obtain this monopoly and will use it against you i.e. via taxation or when you are/do something your state thinks you shouldn't - often among them: Being gay, black, white, Jew, Christian, Muslim, raped, communist, capitalist, rich or poor.
How is this idea of personal property a reasonable reply to criticisms of capitalism? Capitalism is about private ownership of means of production and core resources and is a mere subset of the wide range of economic structures that include personal property.
https://en.wikipedia.org/wiki/Thomas_Sowell#Reception