>Never mind that it wasn't elemental mercury and was perfectly safe to ingest…

I’m sure you didn’t mean non-elemental forms of mercury are safe, but to forestall someone’s taking that meaning: “Organic” mercury compounds can be far more toxic than elemental mercury.

See dimethyl mercury [1]. A single drop exposure (through a latex glove) killed a scientist 10 months after exposure.

[1] https://en.wikipedia.org/wiki/Dimethylmercury

Agree with your post, the amount of thimerosal (Hg-based preservative) made it a non-issue in vaccine safety.