Seems a rather illogical article with a more illogical title. Take the first quote.
So, if any bishop…confiscates any property from anyone, thinking he is protecting his own church, let him be suspended by his patriarch for a time, having first restored what he took away.
Not socialism. Theft. Abuse of power.
St. Thomas?
Now the reason why these people are heretics was because severing themselves from the Church, they think that those who enjoy the use of the above things, which they themselves lack, have no hope of salvation. Therefore it is erroneous to maintain that it is unlawful for a man to possess property.
Again, this is not socialism, which does not have any teaching of salvation. Also, Gnosticism is not socialism. In the second paragraph, the author writes, “While the word “socialism” only found its way into common parlance in the 19th century, its underlying philosophy dates back several millennia.” He then goes back to show some (and different) philosophies which have some tangential relationship to socialism that have been condemned. Not once did he even attempt to show his primary premise, that is, that all of these things have the same underlying philosophy, which I for one do not believe they have.
I think his attempt to attack a more intellectual approach by others fails simply because it overreaches. There is no need to go back in history. We have direct condemnation of socialism (pure socialism), and condemnation of some of the major tenets of socialism. That should be sufficient, unless the intent is to discredit Catholic social teaching as well, which has some parallel with socialism, though a vastly different foundation.
It is no surprise that he ends the article with current politics, even though the direction he took has no bearing on the rest of the article. Not one of the people mentioned have shown to have an underlying Gnosticism, or have condemned all ownership of property as immoral. His title hints at this complete disregard for logical consistency. The definition of socialism cannot change in every paragraph.