Well, it's an online opt-in survey so you have to keep that in mind. Also, they didn't directly poll on the question of background checks, which is the subject that gets the 80 - 90% approval rating in other polls. Instead they asked about the effect of "currently proposed White House legislation" and got a much different result.

Those are true points. I just wanted to point out that there isn't necessarily unanimous support for increased gun-control amongst LEOs. And regarding the FOP, I don't have a citation handy, but I'm pretty sure I've heard that a lot of the rank and file police officers differ with their leadership on gun control issues.