TDK is just the latest in a line of films with unsuitable content for children being rated by the BBFC so that children can see them - this is perhaps the worst instance so far, simply because it has such mass appeal.
I think the BBFC are missing/ignoring their purpose as the public see it - which is the protection of children and other vulnerable people. If everyone can see a 12A cert film, then it should be suitable for everyone. Simple as that. If the BBFC don't understand that parents want/need simple & effective certification, they need to think again.
The BBFC are also (increasingly) not playing by their own rules. I can't find the quote, but they've always said they classify for themes as much as content. I can't think of a mainstream movie as dark as TDK below 15 certificate EVER. *** Waits to be corrected ***
Looking at the BBFC's bullet points, I can see all of those in TDK to a greater or lesser extent. Some of it is implied, but obviously that still contributes to the overall theme.
I'm happy with the principle of a 12 certificate, but I just don't see the need for it to be open to all ages. And I certainly don't see the need to give in to pressure (from parents or the industry) to have a 12A certificate just because the Americans have PG-13.