It is my opinion that Mother's Against Drunk Driving hates the pesky United States Constitution. Read about why I might think this is the case in the interesting blog post "MADD: Lawyers the Cause of Continuing DUI Fatalities".
Everything I read suggests that despite the draconian measures and erosion of constitutional rights, especially when it comes to drunk driving laws, fatalities involving drunk driving has remained constant. It is my opinion that MADD's scary logic is that the continued erosion of civil liberties will eradicate drunk driving, which isn't the case.
It is my opinion that perhaps MADD longs for the days of the Spanish Inquisition - sinners (those who enjoy alcohol) shall be punished to preserve their souls.
Lastly, want to have some fun? Follow the money. An awful lot of taxpayer money goes to programs run or founded by MADD, its affiliates or closely related entities and individuals. Thus MADD has a financial interest in seeing the continuation of the growing industry of "get tough" drunk driving laws.