> Microsoft would remove his poem and nobody would read it ever again. He can only lose.
No, because he retained the copyright. If he won against Microsoft he would a) presumably get a lot of money (financial win), b) strike a small blow for the little guy against megacorps (moral win), and c) still be able to release the poem as CC0 or whatever he wanted (win).
Microsoft would remove his poem and nobody would read it ever again. He can only lose.