Activist: Food producers irradiate food in order to prolong its shelf life.
Conclusion (It follows that)
Irradiated food is not safe for human consumption.
Evidence (Because)
Five animal studies concluded that irradiated food is safe to eat. A panel of independent scientists later found those studies to be seriously flawed in their methodology.
Evaluate
The activist's reasoning goes like this: The only evidence that irradiated food is safe came from five studies. Those studies turned out to be badly done. So the case for safety has collapsed, and thus the case for danger has been proven!
That last step is the problem. Discrediting the studies takes away the support for "safe." It does not add any support for "not safe." After the panel's review, the honest position is that we do not know whether irradiated food is safe, because the evidence we had was no good.
The activist has jumped from "unproven" to "proven false," which is the Famous Flaw of Unproven vs. Proven False. Nothing in the argument gives an independent reason to think irradiation makes food dangerous.
Goal
Look for an answer that says the activist treated the failure to prove safety as if it proved the opposite. It will likely be phrased as a bad move: treating a failure to establish a claim as proof that the claim is false.