You can definitely say “joe rogan thinks an anti-parasitic drug works on viruses.”

I feel like they know this. They’re not defending Joe Rogan, they’re pointing out the very true fact that Ivermectin has, is, and will continue to be used for purposes outside of deworming horses. When you say, “Joe Rogan is dumb because he’s using horse dewormer”, his defenders can (rightfully) correct you by saying “they’re not just horse dewormers, they work for other things too”. When you say, “Joe Rogan is dumb because he’s taking an antiparasitic for a virus”, their only option is to admit he’s an idiot, or admit they’re an idiot.