He should be more concerned with there being too many lefties on the SCOTUS, rather than too many Jews or too many Catholics.
And yes, he's got a point about a lack of geographical diversity on the Court. No way in hell that all nine judges on the SCOTUS should come from only two law schools: Harvard and Yale. There are other excellent law schools around the country that could serve as training grounds for top-notch jurists.
The runner-up to Kagan was Sidney Thomas, a Federal judge from Montana. He struck me as less objectionable than most of Obama’s other choices.