I think he was right not to say anything.
It isn’t as if his opinions on Islam are unknown or have been left unsaid. Anything he might say now will only inflame the situation and cause even more division. Further, by endorsing the project, there are those who might use that to fan an imaginary disagreement on the matter between him and the President as well as the Democrats that have ‘folded’.
There is a reason he is being ignored by the right and the wingnuts on the park51 project. Where he stands on Islam, moderate Muslims and religious freedoms are well known. It is not hard to divine where he stands on the subject..