I saw BASC advising of this a couple of weeks ago. I'm not surprised animal rights extremists are involved.
Near me there's a hunt. It's followed closely by at least three hunt sab groups. Recently one of these managed to obtain a spreadsheet detailing all of the hunts membership. The hunt sab group used social media to advise all hunt members that they can sue the hunt management team for this data breach commenting that they thought the leak of peoples personal details was disgusting on privacy grounds.
The same people also posted a link to a site where the details could be viewed encouraging their members to email and ask why they enjoy killing animals etc. Which shows just how much integrity these people have!