That they are or that they might be? Big difference.
If they are harmful, they should be arrested. But we arrest those who might harm others. Based on a politically driven BAC level, we will take away an individual's freedom, their property, and place their ability to earn an income in jeopardy, all for some harm they might cause.
Is that OK with you? The government arresting you, throwing you in jail, taking away your driver's license, costing you thousands in legal fees, not for something bad you've done, but for something bad you might do? Pretty spooky.