Why adults dismissed the Beatles

Tea. And biscuits.

The Daily Beast is running a series of articles extracted from the book "Yeah! Yeah! Yeah!: The Beatles and America, Then and Now" by respected political journalist Michael Tomasky. Today's excerpt is about why the "serious" press dismissed the Beatles initially. You can read it here.
Personally, I'd like to address a related issue: What was it with the hair? What made otherwise intelligent people (parents of the time) wonder if long hair on boys attracted lice?
Why didn't they think that the boys washed it very often?
How come the New York press in 1964 wondered if the Beatles ever had haircuts?
Didn't they think that boys' hair grew indefinitely and had to be trimmed to whichever length the boy wanted it to be?
Were the adults of that era actually idiots?
Wasn't it enough to watch girls with long hair to realise that long hair could both be washed often, didn't attract lice and had to be trimmed to stay at the desired length? This has me puzzled.