formaldejekyll
How da government initially presented da infamously-toxic preservative --- i.e., it was supposedly safe and harmless like da "good doctor", but then it turned out to be incredibly hazardous, like said gentle physician's alter-ego.
After supposedly "seeing da light" about how horrendously poisonous their formerly-viewed-as-formaldejekyll chemical compound truly was, da powers-dat-be hastily tried to "hyde" behind da false claim dat they hadn't known before how dangerous it actually was.