The humanities are not part of science. They aren't just a particularly soft science, they aren't a science period.
This post on /r/AskHistorians:
History isn’t science and it’s not a science. I find this issue prevalent among people who think that all knowledge is scientific and knowledge that isn’t scientific isn’t knowledge. Philosophically this is untenable, since the scientific method is not itself provable by the scientific method and is a form of presupposition. Methodologically this is untenable since history is not a discipline subject to experimentation. You cannot run repeatable experiments with the data of historical investigation.
This is not a short or simple question, but I will say that this is going to hang on how you are defining science. The response you linked seems to suggest that repeatable experiments are a necessary condition for something to qualify as a science. I do not think this is obvious (actually, I think it is false); you might think that we lack the control necessary to run repeatable experiments in astronomy, for example, but astronomy is a paradigmatic instance of science. I'm thinking here that mere careful observation of natural phenomena can itself serve as the basis of scientific inquiry, rather than science flat out requiring that we be able to rig up precise experimental set ups that we can repeat. Basically, when Galileo looked up and made observations of the moons of Jupiter, he was doing science but I don't think he was doing an experiment in the strict sense of that term. If simple observations count as experiments, then my observation of a Roman artifact should also count as an experiment and we still won't have ruled out history.
Now, it is absolutely right that knowledge needn't be scientific knowledge -- mathematics is a blindingly obvious example. And I think its at least a very plausible view that history isn't science, but again this is going to hang on exactly how you define science. This will be an important thing to consider when looking at sources that make a firm claim one way or the other: How are they defining science?