I'm thinking back through history at causes that social conservatives have supported . . . slavery, prohibition, the war on drugs, etc. and then thinking back at all the things that they've opposed . . . democracy, women's rights, civil rights, gay rights, interracial marriage, immigration, freedom of religion, clothing to wear, etc.
Despite the furor, social conservatives historically always lose in the end . . . but often they manage to cause a lot of pain and suffering before they finally do capitulate. So what exactly is the draw to the movement? What are it's long term goals?
I'll give it a shot :). One clear example is opposing communism. Lenin/Stalin/Maoism was one of the worst things to ever happen to humanity and they were right to oppose it at every turn. In fact I think they may not have gone far enough, and that is a result of living in, traveling through, and observing a number of communist and formerly communist countries.
Another point is that social conservatism is pretty much by definition mostly right, because pretty much all new ideas are bunk. Of course most never leave people's brains, most of the rest maybe get mentioned a few times, a handful get small group followings, but at some point people realize it was not actually that great an idea, with a low rate of exceptions. There are a few cases where they have been absurdly catastrophically wrong, but those are exaggerated by survivor bias (you never heard of the countless times they were right because those ideas never gained enough traction to get heard or remembered) and your strong personal bias.
I also have a theory that those who call themselves social conservatives are those who want to maximize their group's ability to win, which I will say has historically been equal to a group's
population X productivity X social unity. Historically that has been pretty much the only winning strategy, and groups who did poorly at it disappeared. So they have mostly been right. On the other hand, always maximizing those is not necessarily good for individuals or for the species as a whole, which is where liberals in every society fit in emphasizing both individuality and collectivism.
Break your list into the three factors that maximize winning:
Maximize Population:Oppose abortion
Oppose birth control
Oppose any sex except heterosexual sex
Minimal women's rights
Favor immigration of individuals with similar values or who could easily adopt similar values
Maximize Productivity:Oppose recreational drugs and drunkenness
Favor capitalism, with some constraints
You didn't mention any, but historically productivity is proportional to energy expenditure so:
Maximixe oil production
Maximize cattle production (the highest energy form of sustenance)
Most and largest vehicles
Maximal industry
and others
Maximize Social UnityDemocracy may not do this (but it also may)
Oppose excessive civil rights
Oppose gays if they view themselves as fundamentally different to the group
Oppose interracial marriage
Oppose immigration by those who are very different
Oppose dissenting religions
Uniform clothing
Put those together and you can see that social conservatism is a highly effective strategy for a group to win. PopulationXproductivityXunity has been so successful for so long that it is deeply entrenched around the world.
I don't think slavery was conservative. It only really flourished in the New World where the European traditionalists wouldn't be disturbed. It could never have been done at scale within Europe because the populists would have burned the slaveowners at the stake for bringing in thousands of abjectly different foreigners to take their jobs for no pay. The conservative elite would have opposed it because a slave would never have been as efficient or innovative as a person getting paid would have been (lower productivity), and it introduced into society a large group of deeply resentful people with a very different culture (divided populace). It violated two of the three conservative objectives, in addition to the liberal ideals. Basically it was a terrible idea doomed to failure, and it is tragic that the social conservatives of the time didn't squish it before it started. Anybody who thinks slavery was a good idea is an idiot rather than a conservative.