Utterly Mad

it doesn't. when you see guys like Burns walking around who wear bandana's bearing the mark of their Syndicate you don't report it, if your smart that is.
The Syndicate is prominent, and even though they have a rule against killing cops they have no qualms killing someone who reports them to the police. combine that with moles in the police department, an intelligence network, and a virtual army of guys ready to go to jail at the Chairman's word, and they've pretty well intimidated the majority of the people in the city.
The Syndicate has a couple of very obvious insignias they use, though these are usually reserved for the grunts and footsoldiers of the Syndicate, a way to advertise who they are. It's also helped reduce the number of friendly fire incidents the Syndicate has run into.

Essentially, you see a guy wearing something with one of these emblems, you don't report them for a few hours.