It should be stressed that nobody is saying BT is any more culpable than any other Internet Service Providers in this case. They all allow access to the pirating site, Newzbin, but BT has supplied software to other ISPs which allows for the blocking of child pornography and the MPA believes the same technology should block unowned as well as inappropriate content.
Unfortunately it may not be as straightforward as that. Many people believe they should be allowed to see copyrighted movies online free of charge, that's certain. The fact is that unless the law changes they're not allowed at all.
Asking ISPs to take responsibility is another thing. It's a little akin to asking phone operators to be responsible for nuisance callers; nobody likes them but nobody blames BT.
The other thing is that many other organisations would have to either pull out of the UK or start policing their own content. I've drawn attention in here before to the amount of copyright content that exists on YouTube, Search for any Beatles song and you'll find it, quite unlawfully.
Google, at least, is an honest company. What really concerns me is the other businesses - the people who are deliberately making (for example) movies available to every passing downloader.
You can block these if you want, but as people found during the Wikileaks months, they can just move to another server and you'll find you can't get to them. They can play cat and mouse like this for some time before they give up.
As I said at the outset, the ramifications for the legitimate companies will be huge. Ramifications for the crooks - well, they're crooks, they'll just work around it.