This is much ado about nothing. The radio guys in Seattle have been trying to turn this into a scandal, but I think Mike & Mike on ESPN got it right.
The Hawks are just trying to send a message that a$$hole fans who get drunk before the game and who then publicly threaten 49'ers fans will not be tolerated. There's no "entrapment" here, either.
How is this any different from a cop hiding behind a billboard waiting for a speeder? It's no different IMO. "Normal" fans who want to give a good-natured ribbing to 49'er fans can still do this -- just as most cops will ignore you if you're going less than 10 MPH over the speed limit on the Interstate. But if you cross that line and are going 100 MPH, then expect to get a ticket.
What *IS* ironic is that last year, there were a number of altercations between Hawks fans and 49'er fans, and guess what? The perpetrators were mostly off-duty police officers who had been drinking all day!
I really think the intent was to get fans to "self censor" their own behavior. If so, mission accomplished!