Why did Michelangelo decide to portray his David nude?

In Michelangelo's day, the human body wasn't something to be either embarred about or ashamed of. He sculpted it in a tribute to what he considered one of God's most exquisite and glorious creations...Man. That's not a chauvinstic pig's viewpoint, merely a statement of the attitude the way it was then. He was influenced by the Greeks and it showed in his statue of David. Check out the Pieta for another absolutely beautiful tribute.