http://www.ice.gov/about/offices/homela ... tigations/ICE are the group who intercepted Scott Kennell. Everything that crosses the U.S. border is under their jurisdiction, this includes the activities of U.S. citizens who go overseas and engage in unlawful activities and images that are transferred electronically. They have considerable powers and will use them.
While someone named by NTM, IHART or any other investigating team as a sexual abuser/offender should not be on Facebook, I think unless there is a conviction then it is a legal grey area.
However bringing ICEs attention to individuals named in investigations is a positive move, after all NTM has stated that they report their findings to law enforcers (bearing in mind that there are many branches of law enforcers, each with different interests and powers).
Perhaps the matter would be best referred to Facebook or someone with legal expertise in such matters.