What happens if Trump goes and speaks?  First, he gets either boo'd or the crickets effect.  Also, can't imagine where he might draw humor from over what he's done and doing.  Jokes about Muslims, transgenders, race relations, even Obamacare etc. would land with a thud.  Then, he'd get compared to Obama's cool and really gifted witiness.  He can't win by going.  As someone else said, the decision not to go might be the best of his short administration.