it does not bother me when police officers do this... i apply the Deuteronomy 25:4, 1 Corinthians 9:9 and 1 Timothy 5:18 principle here...
"Do not muzzle an ox while it is treading out the grain."
i see it as the officer benefiting from his labor... just like i would not fault a grape picker from eating a few grapes while he's working...