The thing that really defeats the ivermectin argument is simply effect size (or, equivalently, drug effectiveness). For a drug to be useful, it needs to have a larger effect than existing therapies. The larger the effect, the more useful. And the larger the effect, the easier it will show up in studies.
Ivermectin's trial results are mediocre at best. So it can't be that powerful a treatment. It's probably helping a bit, or at least not hurting, but it's not a wonder drug. We'd have seen that if it were!
So then you get into the usual lines of bullshit, as we saw before with the hydroxychloroquine people. "Augment with unicorn horn dust" and "dose more" and "dose earlier" and all that. But COVID-19 is the sort of disease that is impractical to dose too early, so "must dose very early" just means "drug is useless".
Thus the facts are clear: even if ivermectin works, it isn't useful. It was a great hypothesis to test. It failed in the clinic. So it's irresponsible to continue beating against it when we have better avenues to pursue.