Healthy dose of skepticism

For the last couple of days, I've been studying for an art history exam that I have this week. As I've been doing so, I'm getting increasingly frustrated. We're talking about prehistoric through Egyptian art in this section. I'm frustrated because it seems that both my textbook author and my instructor make definitive statements without the evidence to back it up. Now, I've got a background in Archaeology. I prefer to look at all the evidence but even after doing so, I prefer not to make definitive statements about what happened. There's too many variables. Statements like "The figures in the cave painting must be women because they're wearing skirts and holding hands" or " Cave paintings were only done inside because they were sheltered spaces that the individuals can return to" piss me off*. You can't ascribe current fashion trends (skirts) to a prehistoric culture...later art from Persia indicates men also wore skirts. And cave painting might have been the only thing to withstand the test of time, the absence of evidence does not mean that prehistoric cultures didn't create art outdoors, it just means it may have been destroyed.
Now, I'm glad that this kind of thing annoys me. I'm amazed at how my classmates just blindly accept whats being given to them. A friend of mine in the same class was telling me the other day how now she's rethinking everything after I went into a tangent about the archaeological record. My main concerns are A) why don't my fellow students question more and B) why do professors get away with incomplete teaching? If these people are used to this kind of thing in just their classes, what must they be like in the real world? It's more than a little dismal to think about...
*I know I promised to write about more happy topics but this sort of thing really concerns me...