Social sciences are most definitively on-topic.
It's possible to write a good objective answer about any social science topic that has been covered, if you try hard enough. Studies have limitations. Good studies even outline them. Bad studies have flaws. A good answer will need to point those out, explain the contradictions, etc.
Basically, the same rule applies here as would if you were to answer a natural science question where we don't know the answer yet: stick to what we know; don't speculate
The problem with the question you referenced is that each answer would be a different take on the definition of "biased." Some people will go for the radical approach and say that there is no such things as unbiased. Others will go for a more moderate position, and point out that you can achieve reasonable impartiality and point to institutions like CBC and BBC. And then, there's many positions in between.
Ultimately, that question was really about asking everyone's opinion on the subject. That's why it was closed.