Peter Singer belongs to the rare breed of fearless thinkers who do not flinch and go wherever the argument takes them, to the very limit. People who are uncomfortable with this mode of discourse should stick to heart-warming tracts preaching self-improvement and universal love. I have nothing against universal love, I simply prefer to deal with doctrines that yield themselves to rational analysis. When the lesser critics who revile Singer yell that infanticide is horrible, I tend to agree, but I still want to ask, why?
Somehow nobody - not just the lesser critics - seems to have noticed that Singer builds the most compelling case against racism and every other hue of bigotry that could be found almost anywhere, provided one accepts his utilitarian premises. This alone deserves our gratitude. If this line of argument moves him to include animals into the ethical space, so be it. I think that Animal Liberation is Singer's best book, precisely because its scope is limited to bigotry, whether within the species or outside it.
Unfortunately, the liability of this logical approach is that the logician takes himself too seriously. I once came across a bumper sticker that said "Do not believe everything you think". Singer does, and so ends up with some conclusions that are simply beyond the common sense.
It could be worse, and somitimes is. Singer often writes as if economics never existed, particularly when he deals with the redistribution of wealth. Economics may not be as watertight as physics, but it is certainly more grounded in reality than anybody's ethical system, Singer's being no exception. Anybody who lived under communism or worked for the US Civil Service could attest to it, and I did both.
Coming back to the problem of infanticide: people who would rather brand Singer a Nazi than consider his argument on its merit know very little history. Infanticide as a regular form of birth control was widely practiced in the very classical world that gave us philosophy, ethics, and the idea of the rule of law. We do not have to approve of it to be able to discuss it.
What I find particularly offensive is when people, unable to slug it intellectually, recourse to ad hominem devices, like dragging Singer's sick mother into the discussion. Peter Singer is selling us a doctrine, not a personal example. Another Peter managed to betray his revered teacher, thrice, and still attained to sainthood in the end.
All in all, I found reading this book immensely rewarding, if in the end still unsatisfactory. Perhaps utilitarianism is a lot like democracy: pretty bad until you consider all the alternatives.