I never understood putting so much money and effort into eradicating polio until I considered Exhibit 1* here:
I view the eradicating factory farming the same way: Once we drive demand (e.g., One Step) and supply (GFI) such that people eat plant-based and in vitro meats merely for economic reasons, we will have done more to alter the cumulative suffering / pleasure balance over the next X number of centuries than anything else that I think is reasonably on the table. (Except the Singularity, of course! :-)
More on how to get there here.
*A little more explanation: This graph represents two options:
1. The cost, over time, of control (in blue), or
2. The cost, over time, of eradication (in grey).
If you pay a lot at first to eradicate something (the grey line), your costs go to zero. If you just control something (blue line), costs are initially lower, but never go down. It is like paying $100 up front for something, or paying $20/year forever.
In other words, it is worth it to invest a lot now in veg promotion and veg proteins, because the payoff over time is huge!