It's not about being anal. The lighter weight and smaller size is something that I actually find useful for work. If the new lens were all metal and heavier, it would make a difference to me since my regular load is four lenses and two bodies. I take the 2.8 if I have to. And the f4 lens is a mix of plastic and metal. I'm sure the many 70-200mm F4 and F4/is owners can chime in.
Sorry, but KR wouldn't know a fact if it bit him on the ass. While I don't have a 70-200mm f/4L IS, I do have a 70-200mm f/2.8L IS II, and KR indicates that the parts of the barrel of that lens are plastic as well - they certainly don't seem to be, based on thermal transfer compared to lenses with known plastic barrels, such as the EF 100mm f/2.8L Macro IS.
that the barrel is metal, as does PhotoNotes