It's more than that.
Gonzalez, a former Democrat and moderate that Bush has personal relationship with, argued for Bush to back down on opposing the U Mich racial quotas, is friendly towards affirmative action, has never shown any concern with Roe V Wade and other rulings on social issues. I've seen nor heard anything from him that he shares our concerns over judicial activism.
It's well known that anyone or anything not explicitly conservative ends up becoming liberal when exposed to Washington DC for a long time. Given his track record, we can expect no better from him that what we got from
O'Connor, and risk even worse.
Stevens, Souter and Brennan were picked by Republicans. In all three cases, the nominees weren't properly vetted ideologically. This is a similar case.
Far better for us to pick a sitting Federal Judge, a known quantity rather than a judicial 'pig in a poke'.
Bush has made outstanding choices so far and he's told us what kind of Supreme Court justice he likes. I trust him not to screw this one up.