It looks like Barney Frank is attacking Justice Anthony Scalia because Scalia has a principled view on what is and what is not within the courts power to do.
Specifically, Frank called Scalia a “homophobe” in an interview with a pro-gay web site. Turns out that Scalia doesn’t believe that it is up to the courts to decide about gay marriage, but rather it is up to the legislature or up to people to change the constitution. Please note: Scalia hasn’t taken a stance on the issue of gay marriage, only on whether the courts should decide such matters. But that doesn’t stop Barney Frank’s ad hominem attack.
By the way, since when does the federal government decide who can and who cannot get married? You will note it is not against federal law for brother and sisters to marry. It is against state law. The issue of marriage should not be a federal issue. It rightly belongs as a state issue.