I hate liberals as much as anyone, but the SCOTUS wasn't deciding on the issue of gambling. This was a states-rights issue.
Conservatives tend to support states-rights. Liberals tend to oppose states-rights. As such, it is no surprise that the 2 most hard core liberals dissented. However, the fact that it was 7-2 is the Supreme Court equivalent of a sports blowout like Celtics-Cavs yesterday.