Perhaps you meant to type 'sound' rather than 'valid'.
Also, I didn't claim that you had made any "capitalism vs socialism" simplification. I merely agreed with spinfreebob.
I can agree with him without necessarily disagreeing with you, which is what I did.
There are very many quite intelligent people who are liberal. Some of these people are scientists and philosophers who are quite astute at arguing logically and rationally from their starting premises.
It would be silly to make the claim that their arguments are invalid or that they are just plain stupid or ignorant.
The only reasonable cause for them to be as intelligent as they are and still liberal is that they are starting from faulty premises. Either that or you have to assume that there is some sinister conspiracy whereby they know they are arguing illogically, but are doing so to advance some nefarious agenda. I used to believe that, but now know that is a nonsensical position.
Absolutely certain premises are very difficult to come by. Some of the best thinkers like Descartes thought hard about this and came up with precious little, e.g. I think therefore I am. So it is quite reasonable to assume that individual humans with limited knowledge will support different starting premises. To my feeble mind it makes more sense to question the premises of liberals than their logic or their ulterior motives.
Linking to a source that actively seeks to make bad arguments appear good in order to create a difference in semantics? That is called “argumentum ad verecundiam”—a logical fallacy, for the record.
No deceptive arguments are valid, by the definition of validity—which is a synonym of soundness, if one looks in a dictionary or thesaurus.