Partially agree, but I think a lot of the public outrage is over the use / killing / botched experiments on monkeys, which are widely acknowledged to be among the most intelligent and human-like of non human animals.

Regardless of the degree to which it can be philosophically justified, intelligence and human-likeness (in terms of social abilities, emotional capacity, self-awareness, etc) are often seen as making mistreatment more ethically questionable than it would otherwise be.

In terms of scale, factory farming is obviously far more messed up. But humans don't always react purely to the scale of suffering, we also react to its severity and what it reveals about the person who is causing the suffering. Unfortunately, a lot of people are not prepared to see animals who undergo factory farming as enduring "pointless" suffering, while a monkey killed as the result of a failed experiment does, etc.