Congratulations on the site. I agree with your basic principle that it is up to everyone to make up their own mind. What concerns me is the way books like this creep into the conciousness of society. Yes it is only a book, but I have just heard that Channel 4 (one of the main UK TV channels) is showing a two hour programme on Thursday called "The Real DaVinci Code". The programme is a "quest to see if the DVC makes any sense..." I hope it will debunk the book but the fact that the programme is even made gives credence to those who believe in conspiracy.
I started the book with some reluctance. I finished it with gritted teeth in the same way my son & I watch Steven Segal movies: unable to believe that such a jumble of cliche, hamfisted plot, paper thin character and badly researched histoical, geographical and technical information could be the number one best seller.
So, it does matter... ignorance is a weapon of mass destruction.