The FDA was sued and lost (or at least agreed to a settlement) over those comments, which were consequently deleted. Ivermectin is a human antiparasitic that's even on the WHO List of Essential Medicines. [1] Their comment was akin to saying that amoxicillin is a horse antibacterial drug, which is true, but quite misleading. Off-label usage for pharmaceuticals is extremely common and an important right of doctors. I mean that's pretty much the entire point of this topic!
[1] - https://en.wikipedia.org/wiki/Ivermectin