The issue that many constitionalists, libertarians, and limited government supporters have in regards to DUI checkpoints is not that they "prevent drunk driving" because of course no one wants drunk drivers on the road. The issue is that checkpoints are a violation of our forth amendment rights. And if stopping all drivers on the road is ok then so is police randomly raiding old ladies houses to make sure there are no drugs, or patting down everyone who enters a mall to make sure they don't have a bomb. If the forth amendment is not respected there is no end to how intrusive things could get in the name of keeping us "safe" as there are millions of dangers in the world.
Most who oppose checkpoints believe that police don't have the right to stop a car unless they have reason, Ex: the car is swerving. If they are pulling everyone over then it's not BC the car is acting suspicious but bc they are doing it to everyone. It's very disrespectful to both the individual and our constitution to interrupt drivers who are on their way home or work without cause. But most are up set BC of the violation of the constitution it's kind of like that Ben frank quote "those who would give up essential liberty for security deserve neither and will lose both.