So the vivisection experiments would be okay, to your mind, even if all the experimenter got out of them was amusement?

You should be careful declaring that you ascribe literally zero moral weight to non-human animals. It doesn't match up with most people's moral intuitions well at all.

There also exist a lot of non-"sapient" humans, as birth defects and brain damage give us a fair continuum of humans with different mental capacities to think about.