Curious about this act between father and son, a quick search finds that in 1966 the Supreme Ct of Maine ruled on the issue.
"Such kisses are signs of affection, not sexual abuse, ruled the Maine Supreme Court in 1996 when it overturned a sexual assault conviction of an Afghan immigrant who was similarly photographed with his 18-month-old son. The court ruled that the father kissing his son's penis was a common cultural practice and not a sexual act."
"'Kissing a young son on every part of his body is considered a sign only of love and affection for the child,' the court said in its ruling. 'There is nothing sexual about this practice.'"
"'It shouldn't be looked at as a crime,' said Ludwig Adamec, a professor emeritus of Middle East history at the University of Arizona's Center for Near Eastern Studies, who testified as an expert in the Maine case."
http://www.debbieschlussel.com/archives/2006/06/man_bites_dog_b.html
If this is true, Webb has an American court's imprimatur that his depiction is not sexual, pedophilic, but a "legitimate" cultural practice.
As I said, some have a knee jerk reaction and some are curious for new knowledge and want to know the truth.