I have serious problems about this claim. Oh I have no doubt some poll somewhere can back this up, but viscerally it makes no sense.
Are they talking about police chiefs and commissioners, who are largely political appointees, or sheriffs and beat cops? I would wager the answers would be radically different.
We know the reality, Chiefs and administrators know "Numbers"
Most likely they are talking about union leaders.
One thing cops do not want is people calling cops every 5 minutes for a shooting they cannot do nothing about it, except burden and clog the LE work. That said, lately they like to clog it with false witnessing too, but that will change, because it is getting ridiculous.
The media would like the public to believe that all "LEO" are firmly for the "AWB". I can't speak for other neighboring counties but our Sheriff has signed the paper work for machine guns in the county in which we live. I've never taken the time to ask how he feels about the "AWB". He did sate at the time he signed the paper work that he didn't care what weapon a law abiding citizen had, (as long as it was legal) he was glad to support the second amendment rights of all the citizens of this county.