Does gridlock defeat special interests, or serve them?

At the Cato Institute, Marcus Ethridge writes (PDF) a celebration of good old-fashioned government gridlock. By making government so inefficient, he says, you make it unlikely that special interests can dominate the decision-making process:

A large and growing body of evidence makes it clear that the public interest is most secure when governmental institutions are inefficient decisionmakers. An arrangement that brings diverse interests into a complex, sluggish decisionmaking process is generally unattractive to special interests. Gridlock also neutralizes some political benefits that producer groups and other well-heeled interests inherently enjoy. By fostering gridlock, the U.S. Constitution increases the likelihood that policies will reflect broad, unorganized interests instead of the interests of narrow, organized groups.

This seems overly optimistic to me. It assumes that "well-heeled interests" don't understand how to employ the levers of power in negative fashion as well as positive ones. The United States Senate tried for decades to pass civil rights legislation--like anti-lynching laws--only to be frustrated time and again by a band of Southerners who used the filibuster to great effect. In that case, there was broad-based recognition in American society that it was bad to kill black people, but the filibuster served the purpose of protecting Southern white guys. Who was the "special interest" in that case?

Ethridge never once uses the word "filibuster" in his piece, though, celebrating instead on the checks and balances provided in the Constitution--the filibuster isn't in there--and bemoaning the rise of the regulatory state. I'm not really sure how you honestly examine gridlock (and deride the "rent seeking" associated with unelected regulators making rules for the rest of us) without dealing with the ramifications of the filibuster. There's an argument to be made that the filibuster so constrains Congress that the legislative branch has ended up deferring to executive branch rulemakers to get stuff done instead of doing their jobs. The framers of the Constitution may have created a limited government, but they also wanted it to be energetic. The filibuster, as currently used, is a gridlocked step too far. And I see little evidence it serves anybody but small interest groups.