Opponents of gay marriage want strong families with good environments to raise children.

Opponents of drug legalization want to prevent the individual and societal harm caused by drug use.

Viewing opponents with that perspective helps find more effective ways of working together.

It's also interesting that advocates for those "liberal" items want to get the government out of individual choices, which is the same goal cited by "conservatives" against centralized health care/education, etc.

Otherwise every decision would just be made through a review of data and only the first country to make a massive change would be venturing into the unknown while everyone else could simply observe what happens and decide to follow suit if the outcome is favorable.

Being in the US you see identity politics quite clearly. People simply vote by who supports abortion and who doesn't. To them the rest of the platform doesn't matter, but this one issue is so critical that they simply look at it alone and nothing else.

If you look at many of the votes on key issues you will notice that they aren't passed 90 to 10, they are usually 55 to 45, if you are lucky, or even closer. Given how close these votes are it's a surprise anything ever changes at all.