I didn't see the program but would there be the same furore if it was a communist appreciation society? Should we, in these times, not expect one sided journalism from the BBC anyway. The 'We love Joseph Stalin Society' would not even raise an eyebrow despite the fact that he was responsible for the deaths of 10 million. Quite disgusting really if you take the time to think.
So what if people decide that particular interest as a hobby, there are things I find completely distateful that are openly promoted in society so, if we are to grant ourselves the luxury of free speech then their views are as valid as any others. The simple question is, have they harmed or encouraged someone else to harm others with their views and opinions, if so, prosecute them, if not then let them be as long as they stay within the law.
Did they cross the line in the program?