True, but they should not have asked him to take it down.
I can think of scenarios where it would be reasonable for the police to ask someone to stop legal behavior - "please stop pissing off your neighbours" - but this is not one of them.
I was asked to remove offending content too. Like OP they admitted they couldn't make me, but it was implied that it would appease the offended party and make things easier (for them, at least, since it makes it more likely the crank would stop wasting their time).
It certainly wasn't suggested in the way the Mafia might suggest you pay for protection, if that's what you're thinking. There was no sense of authority when they asked it. It sounds like the same thing happened to OP.
Honestly I think it is fairly problematic for them to even relay the request that you take it down. If the aggrieved party has an issue with what you are saying but you are operating within your rights and the law, then the aggrieved party can make the request themselves.
I think that having the police, or a politician (http://www.washingtonpost.com/wp-dyn/content/article/2010/09...) or any other member of the government relay those requests is out of line.
It's pretty scary getting a phone call or visit from the police, but they make it quite clear you're not in trouble, at which point it's mostly infuriating that someone got butthurt enough to trouble you in this manner.