Factory farms have a large net loss in utility due to the suffering they cause animals. If you do not value animals, then it's not surprising that they wouldn't cause a large loss in your utility function. However, from the perspective of wanting to prevent harm in all sentient beings, they cause a large negative utility.
To assert that animals experience qualia is hardly an uncontroversial claim.
This is an offshoot of a thread I made earlier, but which wasn't eliciting the sort of responses I'd hoped for.
So let me pose a clearer question with less potential to get people on watchlists.
What legal ways of making a profit are the most anti-altruistic, the most damaging to society, the opposite of effective altruism in result.
I am using utility loosely. The answers need not be given from a utilitarian perspective at all, but instead merely deal with any means of making a profit that seems to you clearly wretched, and such that the world would be better if nobody participated in it.
I'd also like to emphasize that these things should be legal. There are some obviously wretched illegal businesses that would top the list otherwise. If something is legal but only in a particular jurisdiction, then you should only discuss it within the context of the jurisdiction where it is legal.
If it's a grey area, go for it, but extra points for society-harming enterprises definitely legal in both the letter an the spirit of the law.
This is NOT about whether the enterprise in question should be illegal, just whether it causes a net loss of utility (deal with counterfactuals however you see fit).