I'm not certain, but if I had to guess, I'd say the problem is the media.

I read the article. It goes on and on with "titillating" details about 'slaves' and "branding" and "vulnerable positions" and all kinds of crap - which is all legal, especially between consenting adults.

But they never once say this is what the defendants are being prosecuted for.

My guess? They are being prosecuted for tax evasion or postal fraud or something - and the media gets a whiff of the BDSM aspect and goes nuts with that, ignoring the real issues of the case.