deejayone, I think you may be overestimating the power of the mighty interweb a bit.
Sure, the net is a great resource for quick and easy communication. But think about your comment about email. Half the email traffic out there is spam. Do people take it seriously? No, they bin it.
Same is true for internet forums. I bet that every company/product out there has had someone slagging them off on an internet forum. I've read completely false comments, with ridiculously over-the-top titles, all over the net. A seven-page thread on a forum is NOT going to have any major impact on a business. No more than someone standing in the lobby and screaming about bad treatment. Heck, that would probably have a bigger impact than comments on a forum.
The internet - and particularly internet forums - is notoriously full of bull. Massively successful companies have internet hate campaigns against them and survive the deadly onslaught. A "Cineworld is evil, the dirty scheming criminals!!!!!" thread will have next to no impact on them.
The evidence in the thread isn't enough to convince that Cineworld - particularly as a wider orginisation - are doing anything wrong. If, as you say, people won't even read it and gain a negative reaction just from the title and the tone of the OP, then those are the people who will be similarly swayed by a big colourful advert promoting Cineworld.
If people don't care about the evidence in making a decision, businesses have little to worry about. All businesses know they cannot please everyone. If evidence is important, then this forum thread will have little impact, if any at all.