Let's Just Keep It As Clean As Possible: Minimizing Confrontation

Let us concede that engineering animals with not just human DNA or cells, but with human organs, is okie-dokie.

Then let us suppose that we applied that concession even to engineering animals with "human" or "partially human" brains (so that we can know how human brains work). No problem; that's consistent.

Let us then suppose that an animal with a brain "nearly completely made of human brain cells" began, fantastically, to display human-ish behavior.

I would suppose that two things would have to be done. First, all such experiments would have to cease, at least pending deeper knowledge. Second, the life of this animal would have to be preserved in as dignified a way as possible.

That's what I'd suppose. But apparently not.
Stanford law professor Hank Greely, who chaired the ethics committee, said the board was satisfied that the size and shape of the mouse brain would prevent the human cells from creating any traits of humanity. Just in case, Greely said, the committee recommended closely monitoring the mice's behavior and immediately killing any that display human-like behavior.
What the hoody-hey?! If they seem human-ish, kill them?! But that's no surprise.

Here's the real foundation: the most important thing is to gain knowledge; it is more important than life. Plus, if we let the thing live, then we'd have to put up with freakish activists wanting to free the thing. Oh, how messy.

You want to know what this is? It's not concern for mankind. It's curiosity. And it's not just curiosity, it's diabolical curiosity.