Pat is so entertaining. I still wonder if he was just joking.
Leaving aside the demon idea
, being more careful about thrift store stuff is a good thing.
I was a recessionista before the recession. I find amazing things at thrift stores. But I keep all thrift store clothing in tight plastic bags when I bring it home, and treat everything before I bring it in from the garage. Hot water wash and high-heat tumble dry for the items that can tolerate it. Kill-boxes primed with ammonia pads or other toxins that won't harm the materials, but will kill anything living in the fibers. Minimum quarantines for all items, just to monitor them. Strict cleaning afterward to remove any poisons.
Why? I've worked at several thrift stores. I won't scare you with the things I've found in clothing and household items. While most of the big chains prefer that items are cleaned or laundered before donation, it doesn't always happen. Most items go to large processing centers where they are loaded into big crates and bales before being shipped to individual stores. Infestation from one item can quickly spread to others. Smaller local stores may claim to throw out or donate anything that isn't laundered, but it often sits in a back storage room until the donation or trash truck arrives.
So listen to Uncle Pat, just substitute 'critter' for 'demon', and reach for the ammonia instead of the Bible.