By “I Would Do” I don’t think he was volunteering to be violently, needlessly humiliated and treated like a criminal on the street for his skin color. Seems like “I would subject someone else to something I would never agree to” is a perfectly reasonable interpretation of Trump’s words…
Sure, but he couldn’t say, “People accused me of taking drugs, I’m willing to take a drug test.” No, he had to project that onto Hillary. (Assuming that he was volunteering to take the test and not administer the test.)