Bad slippery slopes again

If we permit homosexual marriage, then we'll permit polygamy, and polygamy is bad! Therefore we shouldn't permit homosexual marriage. That's been a cry of the Right for months now. And it's a terrible argument form, of which the Left is also very guilty of employing. There's some big controversy about a bill that's working its way through Washington right now that would make it an additional crime to hurt or kill a fetus on an attack on a pregnant woman. It's an interesting question, whether that law is appropriate or not. I don't have a strong opinion either way. But other people do, and it's not because they've thought it through more carefully. The Democrats are up in arms about this proposed law -- but not because they disapprove of double-counting for a single assault, or because they don't think that a fetus is a valuable thing that should be protected by law. Rather, they think that the law would lay the groundwork for the undermining of abortion rights. To match the above form: If we criminalize harming a fetus in an attack, then we might value the human fetus too much and overturn Roe v. Wade. And overturning Roe v. Wade is bad! Therefore, we shouldn't criminalize harming a fetus in an attack. More shocking still, the Democrats actually admit to this motive, and base their rhetoric on it:

But by giving new legal status to a fetus, it "will clearly place into federal law a definition of life that will chip away at the right to choose as outlined in Roe v. Wade," the 1973 Supreme Court decision that established a woman's constitutional right to an abortion, Sen. Dianne Feinstein (D-Calif.) said.

I haven't read Roe v. Wade in a long time -- I don't remember whether it includes a stipulation as to whether a fetus is alive. If it did, and the bill contradicts it, then it's unconstitutional and someone should say so. If it doesn't, then Roe doesn't depend on such a definition. In general, slippery slope arguments are just plain bad. If there's something wrong with the *bill*, then say what it is. After all, if there's *nothing* wrong with the bill, and it's a just law that should be adopted, AND, as the Democrats are alleging, it would undermine Roe v. Wade, that's at least a prima facia case that Roe v. Wade ought to be undermined.