Which one of the following most accurately expresses the main point of the passage?

I am confused as to why answer choice E is incorrect. I initially interpreted the general principle that no true work of art is obscene as a premise for the senator's conclusion that there is no conflict between the need to encourage free artistic expression and the need to protect the sensibilities of the public from obscenity. This conclusion would not follow from this premise because there is no guarantee that encouraging free artistic expression would always result in true works of art. I viewed the senator's justification of his principle in the face of the counterexamples as irrelevant because the counterexamples discuss well-known works, which are not works of art per se. I chose E because I thought that the senator was trying to justify a position (what I perceived as his conclusion) by appealing to an irrelevant premise. Why is this reasoning incorrect, and how can we be sure that no true work of art is obscene is the senator's conclusion despite the word thus in the second line?