How to enter graduate school in a social science discipline from a computer science background?
I am not totally familiar with how social science graduate programs work. But, in general, in order to have success with grad school applications after your undergraduate: (1) you should show you have the theoretical knowledge needed to succeed in your research and graduate studies (2) AND you should show some hands-on experience, at least tangentially, related to the area of research and study you want to pursue.
If you want to get into some interdisciplinary areas like computational social science, e.g. social network data analysis, your computer science background is a definite asset that definitely helps you both get into the program and get ahead in your studies. If a program of choice is interdisciplinary enough, they may not care about your lack of coursework in humanity or suggest you take prerequisites as part of their program.
However, if you don't want to &quot;beat around the bush&quot;, so to speak, and get into more theoretical and pure social science fields, I think you need to take the essential coursework similar to what students with those majors take. Having research in social science beforehand also would work if you can allocate some time for that. It may require you to take an extra year to take all the extra credits but I argue that it also benefits you and increases your success in grad school, even considering the fact that you are a self-studied and well-versed person in social science. Grad school is not often a good place to catch up with fundamentals. I think it is important to take your time and build the foundations before starting your grad school studies.