> I think it is safe to say that those brains are having a blast

How could you possibly say that? You are positing that the brains are both conscious and happy. Both of those are leaps.

> It just invokes a strong emotional response because it's so "abnormal"

You are making an assumption about why people find this horrifying, and the assumption you made was uncharitable.

> OTOH, this is HN, I guess. Having empathy for real people would be harmful to the business model of most people's employers.

I do not see how people on HN being horrified by human brain experiments means they do not have empathy.