People suffer and die from things that animal research can help us study, and I don't think that killing a dozen or a hundred or a thousand rats per lifetime we save is too many. (A human lives about 30 times as long as a rat, and Id say a human year is worth 30 times a rat year. A little self-centered, but probably not genuinely that awful.)
Something like 600,000 people in the US die each year of cancer. If you figure on average they'd get ten more years, that's about 75,000 human lifetimes a year lost.
So Id be okay with a literal rat holocost: 75,000,000 rats a year on the altar of science for as long as we can get useful knowledge about cancer from them.
In actuality, I expect we're killing less than 1 rat per human lifetime lost each year -- and Im so absolutely okay with that cost to make progress against scourges like cancer, it's legitimately hard for me to understand the other view.
Do you really believe that future humans will condemn us for killing less than 1 rat per human lost to try and stem the loss of human potential?
Or is your position that it's just not sufficiently useful to do things about mental disorders (which cause lifetimes of suffering and disability, instead of immediate death)?