Well, sure, I've probably said worse things to my friends in a joking matter. That said, I wouldn't post on a photo of a friend holding a baby and essentially call him a pedophile. That's crossing the line.

In Australia, this term has been part of the gay vocabulary for a very long time. I've heard it used by gays (in a derogatory sense) to refer to men who like underage males for over 30 years. There is no doubt whatsoever about its use by Alefantis.

If you look at urbandictionary, there are posts from early 2000's that claim chicken is slang for a young boy and young male prostitute.

http://www.urbandictionary.com/define.php?term=chicken&page=3

An underage male who prostitutes himself to middle-age men -- usually married professionals and businessmen -- by standing on certain city >streetcorners known for the "chicken trade." "In order to finance his drug addiction, 16 year-old Otto works 24/7 as a chicken at 53rd and 3rd." >by boutsos May 23, 2005

http://www.urbandictionary.com/define.php?term=chicken&page=2

A term used to describe a young (generally gay) male; often used with connotations of twink. (See also: chicken hawk) Did you see the chicken Ryan brought to the party? That boy was like, seventeen! by jcdj June 12, 2004

http://www.urbandictionary.com/define.php?term=chicken&page=7

A young boy, attractive to pederasts Joe was very fond of young chickens. bumboy #jailbait #little fairy #young poof #adolescent by Edna Sweetlove October 03, 2006

Good question