Steve Kornacki draws the same parallel that I've drawn in the past between Islamophobia and overzealous anti-communism, and also notes that despite George W. Bush's conciliatory rhetoric on Islam, he nevertheless provided credibility to Islamophobes like Daniel Pipes who get outraged over Muslim-American women winning beauty contests.
That Miller, who supports abortion and gay rights, found common ground with Robertson on Bush's war on terror illustrates the political power of Islamophobia for the GOP. In many ways, it has become the glue that anti-Communism used to be: a demon that fundamentalist Christians and white ethnic voters from outside the Bible Belt (Reagan Democrats used to be the term for them) can both agree to curse.
The one thing I would add is that the fact that conservatives approach Islam the way they approached communism does not mean that they are the same thing. Conservatives benefit from a facile comparison between the extremist ideology of al-Qaeda and communism. But the most obvious point is that unlike communism, the takfirism of al-Qaeda is not an existential threat to the United States. There is no nation with power remotely comparable to the Soviet Union under its sway. As an ideology, it holds little appeal even for Muslims, who are its intended audience, because it has mostly resulted in the slaughter of other Muslims.
As far as Americans are concerned, ultimately the people who find these kind of categorical objections to equal rights for Muslims compelling enough to vote for them would probably be voting Republican anyway. Islamophobia isn't "the glue that anti-communism used to be" because it's still the same glue that overzealous anti-communism was, which is a hatred of liberalism that refuses to make any distinction between liberalism and communism, and now is attempting to do the same with liberalism and Islam. The right's Islamophobia is like the right's overzealous anti-communism in the sense that's it's really just a medium for explaining to the masses why it's important to destroy the same domestic enemy the right has always seen itself fighting.