Well there is the British
Board of Film CLassification but I doubt discrepancise in book to film characterisation or the rule of engagement in a fantasy world would particularly bother them. They are more concerned with things that "might frighten the horses".
As for what the Prof would have thought ... well I think he would have started spluttering into his ale long before - possibly when he saw that Frodo was being played by someone who looked 12. Apart from perhaps Boromir and Eowyn, I think most of the characters were demeaned by the character simplification required by a plot driven film. Legolas and Gimli suffer most probably especially when their key points of use in the plot (Moria and Lorien) have passed. The serious Gimli becomes comic relief and the reflective Legolas becomes Captain Obvious. It is the nature of the beast....
The orcs are one of the more problematic issues in Tolkien generally and one he struggled with. The film simplifyu this by showing them as being spawned and not as I recall including the Cirith Ungol orcs aspiration to lead a quiet life when the war was over. Even with the portrayal of orcs as sub-animal let alone subhuman the killing game of Legolas and Gimli is something I found uncomfortable in both book and film. But this incident seems fairley trivial in comparison with Aragorn killing an ambassador during parley .