I know that it is inconvenient and also I don't know why they had to detain him, but testing a driver for alcohol should never be something bad or maddening. If he is so tired that he can cause an accident and drives as if he were drunk, he should not be driving. And the police have every right to test him.
(But that doesn't mean they need to be assholes about it and detain him or any similar crap.)