You're a freaking cop. It's against the law. No matter how petty, as citizens of this country and the states and counties we live in it's against the laws we are asked to abide by. Don't like it, move somewhere where it is legal, or rally and vote your prospective law changing politician into office. It's not bullshit to arrest someone for having illegal drugs on them on top of other offenses. How many offenses in the same stop until it's "ok to arrest them"? All you're doing is taking responsibility away from the idiot that knew it was illegal and still decided to carry it.
Yeah yeah, I get there are a million other worse things happening likely within five miles of this stop, but it still doesn't excuse someone from breaking the law no matter how petty people see it. Go read the story of that lady that killed two kids because she was speeding in California. We all speed every day and consider it a petty offense, until it kills a little kid or an innocent person and then of course we all act as if it's death penalty time.