Let me just say, I am pro-life. I'm sick and tired of all of this making abortion illegal by making it a Constitutional Amendment. Same for gay marriage (which, in my book, is wrong on all kinds of levels), and human cloning, creation of life should be left to God.
The 18th amendment banned alcohol, Prohibition, to stop the consumption of alcohol and to stop organized crime. It was repealed with the 21st amendment for many reasons 1) While alcoholic consumption had declined, it hadn't stopped. 2) Organized crime wasn't stopped. It existed before, during and after. 3) It was seen as an imposition on personal liberty pushed on the nation by religious moralists. (Sound familiar?)
That said, abortion is a moral issue. The government has no business dictating morals to the people. I disapprove of abortion on the grounds that it is murder, however, that is my view via my religion and I am not allowed to push my religion on someone else, nor is the government. I disapprove of gay marriage. It is a moral issue and has no business being written into the Bill of Rights, nor does human cloning.
The decision to reverse the 18th amendment also gave the states the right to decide if they wanted to allow alcohol consumption. We know how that went.
That is where all of the other issues on moral grounds should be directed, to the states and their legal systems.
The federal government should keep to protecting the borders, regulation of businesses, and improving infrastructure. All else belongs to the states, their legal systems and the personal choices of the individuals who live in this great country.