So, Smith is saying, because we legalized aborting fetuses and because we use embryos for experimentation we are very, very close to extracting organs from living human beings because, you know, "current trends continue."
In other words, abortion and stem cell research are like the "gateway drug" marijuana. One good toke and we're on to sucking kidneys out of quadriplegics. That's basically the "slippery slope" argument in an analogy.
To be serious, Smith's got little logic going on here - at least as far as I can tell from the bit of the article still accessible. The "slippery slope" argument - that we erode the "sanctity of human life" by allowing women or the elderly or the disabled choice in their medical care - is not based in fact or law but fear.
When Christiaan Barnard successfully completed the first heart transplant in 1967, giving Louis Washkansky of Cape Town a healthy heart, taken from Denise Darvall who was rendered brain dead in a car accident, he was roundly accused of "playing God." The advancement of medical technology has always caused fear and dire predictions of our lost moral compass.
I expect Smith is either working to drum up some fear for his own "pro-life" purposes. In his spurious logic, heart transplants and other medical developments did lead to abortion (1973) and predicted the rise of the "euthanasia" movement. And yet we know - and as a society approve of - such medical advancements as heart transplants, stem cell research and abortion because they improve our quality of life, preserve personal choice and rights, increase our longevity, and contribute to our success as a society.
I think what Smith is concerned about is a society moving away from traditional and religious valuations of quality of life - and suffering - that he feels should be legally mandated. Striking fear in the disabled and infirm for the safety of their organs is really not the best way to approach an argument for medical ethics. Facts, rational argument, and application of law would work better. But it is the way of cultural conservatives bent on imposing their values on the rest of society.