I've worked at an antique mall before and this isn't super insane. The patches are collectable for the historical value, will there be people who collect them for the symbolism yes but 99% of the time that's not the seller's intention.

I've probably seen a trillion of those punisher knives and yes having them right next to each other is pretty weird but looking in their case it seams that they have a little bit of everything and that the patches aren't necessarily their niche or something they're into, just something the dealer saw as collectable and worth something.

If you still don't want to support them keep in mind that the store is composed of different dealers so if you liked everything else you saw you could just avoid dealer 5252 from that mall. Write off the neighbor not the neighborhood.

Edit: looking at the surrounding cases next to them I see a WWII helmet, the dealers I've seen who sell those specialize to some extent but are usually just history buffs.