I mean I get Tom is their friend and what not but the fact remains he's a liability. For all they know his brain is hard wired like a camera and the Aliens can see and hear everything they are doing or he's a walking tracking device. They should have sat him down for nice talk as soon as he was walking around and talking then there was the actual metalic bug crawling around inside of him how is that not a red flag? They should at least have him on lock down or have someone watching him 24/7. I mean why would the aliens just let him go?