Genetically bred so they can appear as humans such as the the leaders in our world governments.

considered a threat

"Reptilians genetically bred to enable themselves to appear 'human'. Also less-humanoid appearing Reptiloids who use a form of technosis, molecular shape-shifting and/or laser holograms to produce an outward "human" appearance. Reports of these have surface from underground joint-operational facilities near Dulce, New Mexico; Dougway, Utah; Groom Lake, Nevada; Deep Springs, California; and Fort Lewis, Washington and elsewhere. They are reportedly involved in some type of infiltration agenda. These 'infiltrators' can appear remarkably human outwardly , however at the same time retaining reptilian or neo-saurian internal organs. Often described as appearing 'bulge-eyed' with scaly, hairless skin behind their 'disguise'. One report alleged that the 'Chameleons' may utilize artificial 'lenses' to conceal "slit-pupiled iris'". Some claim they are genetically bred 'mercenaries' who are part of an advanced guard of a planned silent invasion-takeover of human society."
http://www.tarrdaniel.com/documents/Ufology/alien_species.html

Disclaimer: please view this material as exploratory, even metaphoric, if you like.