I don't think he rejoices in the killing of the unborn per se. Let's take a look at that list in the OP:
1. Abortion: Ever since Roe v. Wade, tens of millions of abortions were performed. The traditional and christian view is that all life is sacred, and the killing of millions of the most innocent is an affront to all those who value life.
2. Gay Marriage: For thousands of years, marriage has always been between a man and woman. Now some want to change that. Why? Fairness? Equal rights? They may say it's that, but it's really because they want to break down the traditional definition of marriage.
3. Marijuana: Since the 60s, marijuana use is seen as rebeling against the establishment, which back then was much more moral and God-fearing than today. Now, the establishment is a near all-powerful federal government, but marijuana use is still basically rebeling against the old ways and traditions.
4. Civil Rights: Never mind that republicans are the ones who were responsible for the Civil Rights Act or ending slavery. And never mind that democrats were responsible for the Jim Crowe laws or Ku Klux Klan (i.e. Robert Byrd), or that they tried to filibuster the Civil Rights Act (like Al Gore Sr.). No, forget all that. And forget how Lyndon Johnson and the so-called Great Society took the once strong black people and turned an entire race into a permanent underclass caste and annihilated the black family. And to add insult to injury, they tell them that if they ever try to get out of that miasma and become independent and self-sufficient, they are called Uncle Toms, Oreos, sell-outs, or worse.
No, all that is meaningless because only the republicans can be racists. Democrats can never, ever, EVER be racist. Black...white...doesn't matter. If you're a republican, you're a racist. Democrat? Not racist. They call Nazis right-wingers and many times I've heard them actually call Hitler a christian in order to smear not so much Hitler, but christianity in general. They can't deny the Holocaust (though some do actually try), so they had to change it so that the Nazis were on the right and not the left. Same with Mussolini fascism.
Liberals hate God, the Bible, christianity, conservatives, and the old traditions that they see as being rooted in the Bible. They want to tear down the old traditions and taboos, and any time something happens that's a direct affront to God, they celebrate, not just because they think they won some moral victory, but much more because it's like a giant middle finger in the face of those who still want the country to remain as it was founded. They get themselves all worked up about so-called "Dominonists" or "Theocrats" or whatever that might take over and supposedly turn this country into ancient Israel during the Judges. Funny, they don't seem to have a real problem with Sharia though.
That is what he and the other liberals rejoice and revel in. Not so much the death of millions upon millions of unborn. It's that we're repulsed and offended by it and consider it a great atrocity. They have no problems offending christians and conservatives. They will react like angry bees if the wrong person gets offended in even the slightest way, but us? "Deal with it (usually followed by a bunch of profanity)." In fact, they enjoy it. Why else would the OP come here and post that except to gloat and "rub our noses in it" because he thinks their side is winning?
