Summary: The Doctor has stumbled across a cover-up.
Something fishy is going on here and the Doctor senses a cover-up. Humans aren’t the only people who prefer to hide certain things from the general public.
The Doctor doesn’t hold with that kind of secrecy; if something happens or is being done that might affect the lives or livelihoods of the resident population then they should be told about it. That’s the ethical thing to do, allowing everyone to take whatever action they feel is appropriate.
Governments always seem to think they know best though, claiming they didn’t want to cause a panic.