It's it possible the Chief opposes the idea for a plurality of reasons, and that the race card was the most swaying, in his mind?
Reasons why the Chief might oppose such legislation; It's silly, It does nothing to stop actually indecent exposure, It waists police assets, Anyone who writes a ticket for this WILL be sued, Some construe it as racist.
Pro's of the legislation (if you're a fascist);
It gives the police a easy opportunity to establish a contact, and then attempt to escalate the situation, wherein; the victim could inadvertently surrender some of his constitutional rights. (4th and 5th primarily)
This COULD help if the city is having a problem the gangs. (but it remains a very fascist way to do so)