Answer:
Well, why would <em>you</em> think its not important? Is there a specific reason you would think it is not important? It's really tough to answer things like this because it really depends on your own opinion.
I am not sure what the others thought about it (for example Kahlo and Rivera were communists, so they likely believed it too!)
but a very good answer is <span>B. David Alfaro Siqueiros, since he was very opened about this view, stating it many times. </span>