Anything VPW put together himself and "taught" - definitely.
I wouldn't discount the original sources of the material he plagiarised. Some of those are probably very good. But the twist put on the copies taints the copies badly.
In any event: 1 Th 5:21 (NASB) but examine everything; hold firmly to that which is good
which means, really check it out, think about it in detail, and how it fits with the rest of what you know about the subject and about the Bible in general.
The reverse of "holding firmly to that which is good" is "abandon, discard, throw away that which is false or faulty." I think we do a lot of that, here at GSC.