Brenda Leyland's views about the McCanns aren't exactly uncommon - people I know have ventured that opinion, too. OK they didn't become obsessed or post venom about it online (afaik), but in itself it's just an opinion.
Posting nasty and even abusive things online isn't a crime, in itself. If it becomes criminal it would be prosecuted, usually under the harassment or malicious communications acts. (Aside: BustiKate, at last someone explaining what 'trolling' actually is! Thank you! This annoys me too).
This is an interesting article: www.buzzfeed.com/patricksmith/read-the-deleted-tweets-brenda-leyland-sent-the-mccanns#28tkkha
From what I have read the McCanns weren't even on SM and (sensibly) ignored these vitriol campaigns. I think they have more to worry about than what some rather sad people said about them online, tbh, and they don't exactly lack power. They've been through a devastating loss, and I'm not condoning the vile campaign against them, but they seem to have dealt with it in a resilient way and not to be particularly vulnerable.
Like many others here, I find the trial by media the most disturbing aspect of this. Doorstepping, humiliation on national TV, harassment by Sky media? No-one, but no-one, whatever they have done, deserves that. Does it actually make Sky any better than these alleged online?
And note, nothing has actually been proved. Police were investigating.
We have a justice system, police would have investigated what she tweeted, and her mental health would have been assessed. (I think it's very likely she had MH issues, but armchair diagnosis is a bad idea). If mental health professionals had found she did, of course, it's likely she would just have got a stern warning - and some professional help for her mental health issues.
There were many people out there posting things as bad or worse, you have to wonder why Brenda Leyland was singled out like this. Easy target? Probably.
This was a witch hunt.
In the end this is a tragedy and no-one has gained except the disgusting Murdoch gutter press, which something needs doing about. Sky News have blood on their hands.