So, you agree that the part about 'selecting' cancer cells is not merely physics? Well done: you've just admitted to the usefulness of an inventive step and the value of this innovative method for curing cancer.

Because it makes it easier to close your world-view, which I think is a bad thing. I think it better to have visitors at least acknowledge that other, valid views exist every time they make a search, rather than enable them to categorically filter content they think is unethical.

In my view, it would be tantamount to letting parents decide what subjects their children should not treat in school, on a basis that this or that subject is `immoral' or `disgusting': that looks like a bad thing for education. Imagine having parents basically forbid their children to ever hear about modern biological research, or about the gruesome parts of modern history, just because they themselves dislike it or fear it from lack of understanding.

I am happy that my [European] government has strict rules defining what all students must (at a minimum) see in their schooling, be that in school or at home. I am not very well aware of the policies in foreign parts, but I suspect that American legislation is not quite as strict on that point -- please don't flame me if it isn't.

So if I decide I don't want to see any content from, say, female authors at all, they should implement such a feature for me?

Wouldn't Amazon be promoting misogyny that way? And racism and all kinds of discrimination with just a few extra radio bullet options?

I don't think it is part of their duty to provide such options. The potential for abuse is just too big.