Killing a defective infant is not morally equivalent to killing a person. Sometimes it is not wrong at all.

The notion that human life is sacred just because it is human life is medieval.

I don't understand the notion that modern farming is anything do to with nature. It's a pretty gross interference with nature. I think it ought to be governed by the standards of how it affects the individual animals, just as we'd want to deal with institutions that deal with humans by how they affect individual humans.

To be a utilitarian means that you judge actions as right or wrong in accordance with whether they have good consequences. So you try to do what will have the best consequences for all of those affected.

If you go back in time you'll find tribes that were essentially only concerned with their own tribal members. If you were a member of another tribe, you could be killed with impunity.

Surely there will be some nonhuman animals whose lives, by any standards, are more valuable than the lives of some humans.

If penicillin had been judged by its toxicity to guinea pigs, it might never have been used by man.