It's worth noting that ivermectin is not FDA approved for used in humans against COVID-19. It is approved for humans use *only* "for human use to treat infections caused by some parasitic worms and head lice and skin conditions like rosacea".
It's also worth noting that ivermectin is produced specifically for animals as well, and the use of animal formulations of ivermectin, which are different than human formulations somehow, is the problem.
Reference:
Using the Drug ivermectin to treat COVID-19 can be dangerous and even lethal. The FDA has not approved the drug for that purpose.
www.fda.gov
Conclusion: Calling ivermectin a horse drug is not ignorant nor pushing an agenda. If people are taking the animal formulation of ivermectin, it is a "horse drug".