Should art be able to protest and teach?

I studied visual arts at Douglas Anderson School of the Arts, so thinking like an artist is just being me. When it comes to making art, it's all just expressing who you are at that time; this includes how you feel, what you're thinking, what you want, what you need, what you want to express. A lot of the time art is benign. It'll just exist to exist, the same way an artist exists. Other times, though, artists do want to say something with more impact because they have been impacted by something. Something has made a difference in their lives somewhere and they want to share that with others. At this point, whatever they express through whichever medium they choose takes on some sort of educational or political medium, and not everyone is going to like what they say. Here are some examples of what I'm talking about:

Catholics commissioned great frescoes in the halls of their cathedrals to instruct the poor about God and His Word. Whenever Muslims came through, they became offended by the images of people and animals and painted over the frescoes.

Another comes from the same time period where Michelangelo supposedly painted himself into a painting commissioned by the Pope as a flayed skin. He didn't like the Pope for having him paint when he'd rahter sculpt, so he did something grotesque in this otherwise educational piece.

My last example comes from the play, "The Book of Mormon." As a play, it makes satire of the beliefs of the Latter- Day Saint faith.

Do I agree with what each artist did to teach or protest something? No, and not everyone will agree with them, but they can still speak up about it. Viewers go wrong when they assume the art they have witnessed is some defining truth that needs no context or to be questioned at all. The Muslims that defaced captured cathedrals assumed that all of the images were being worshiped (and rightly so at times), so they protested and made their own art. Michelangelo didn't wanna paint, so he painted himself as but a shell of what he normally is to protest the very painting he painted himself into. The Book of Mormon play is wrong in portraying what the LDS faith actually holds dear and simply pokes at some of the weird quirks we have/had that other faiths don't have, but it doesn't change what we believe or the message we share.

In the end, art is art. You can choose to be offended by it, be awestruck by it, buy it, sell it, deface it, alter it, erase it, add to it, love it, or leave it. It'll keep on doing it's thing, and you can keep on doing your thing.