Possibly the wider issue here is the terminology used by the shipper.
In the Valujet accident, the shipper had described them as oxygen "canisters", rather than "generators". Additionally, the term "expired" (or words to that effect) were used to describe the shipment. This led to the assumption that they were not DG.
When we do DG training, we all learn about the responsibilities of shippers and acceptance staff, but the reality is that shipments are frequently packed/delivered/consigned by people who are acting on the instructions of the shipper. The appropriately trained people are simply too few to follow the packing/delivery/consignment process of every package, and therefore they delegate (some would suggest abrogate) their responsibility. It is therefore an unfortunate fact that many items travel by air every day that have the potential to cause harm.
I am frequently uncomfortable about carrying freight for these very reasons, but it is the crews that carry freight exclusively (freight dogs) that are at greatest risk here.
My only suggestion is that whilst you are walking around the aircraft, take a look at what is being loaded. If something looks like it shouldn't be there, ask questions. If you see something, say something.