The Facebook policy has been around for a while - at least a year or so. They allow pages or communities for almost anything, but advertising is somewhat limited. Their guidelines are pretty clear on prohibited content:
https://www.facebook.com/help/174908809241578/
Your advertisement may have been disallowed because whoever reviewed the application either found language that wasn't appropriate (for example, that could lead to a sale), looked at your community page and saw products for sale (which would deny you the opportunity to advertise), or believed that your community page lead directly to a sales opportunity, which would, once again, bar you from advertising.
They will allow advertising for a community page as long as there's no products for sale (as per their terms of service). This also includes linking to third party websites that sell the product.
As far as rationale? Here's one that's not too far fetched: Facebook is a global site, with users from all over the world; there are several countries where e-cigarettes are outright banned and others where advertising is prohibited. While you could argue that the Ad Manager would allow you to target users of a specific country (or exclude countries), imagine trying to maintain a current list of what is and what isn't allowed at a global level? Much easier to simply blanket ban all of it. Is that the right thing to do? Probably not. Is it the easiest thing to do to absolve responsibility? Most definitely. That's not to say there isn't an ideological issue lurking in the background, but it's most likely a "we don't want to be responsible for content and get named in a lawsuit for doing something illegal in some country where we don't have operations".
