Again I go back to 1964. It was just assumed that society was moral with respect to homosexuality, respect for religion, pro-American values taught in schools, etc. We can debate till the cows come home about whether it is good or bad that these things are now passe. But the average “religious right” activist at the time didn’t have to worry that their basic moral beliefs would be blatantly violated in school. And to put another spin on it, if you told the average democrat in 1964 that their party’s main reason for being 40 years hence would be abortion and gay marriage you’d have been shot on site.
How many average Democrats do you know? I've known a few, some since 1964 in fact.
I don't know any that would agree with that statement, though. Abortion ("choice") is no longer an issue with them, rather it's a buzzword their candidates use from time to time to energize the women who work in their campaigns - the same as "right-to-life" Republicans like to make promises to "overturn Roe v. Wade."
One of the differences I see between the two major parties is the Democrats' always looking for new "entitlements" to add on while Republicans (or at least a significant minority of them) want to refight the battles that were lost decades ago.
Yet, for some reason, even the most conservative Republicans are reluctant to come out and say they would like to abolish Social Security, Mediscare and other social programs (all but one, that is) as not being the proper function of the federal government.
So we have the "theocons" as Gold calls them continuing to wage war against abortion and homosexuality while the "fiscal conservatives" dither as federal spending goes through the roof.
It's looking more and more like the Republican Party better fits your "main reason for being" criteria, after you add in the "strong national defense" platform plank. The party's commitment to limited government is questionable, IMHO.