In the intellectual discipline known as logic, conclusions are based on premises.
One of Herek's premises is that people who volunteer to look at child porn are a truly random sample of persons - a foolish notion.
Another premise of Herek's is that miniscule samples using widely divergent methodologies can be extrapolated into one homogeneous result for a population of millions - another foolish notion.
Another premise of his argument is that selecting only three surveys with widely divergent methodologies from the entire literature available is good research - yet another foolish notion.
A conclusion which is based on even one false premise is valueless. A conclusion based on a variety of false premises, as Herek's is, is more than valueless - it is shameless propaganda.