A troll or other miscreant who jumps into an online group or forum, usually to push a view that is contrary to that prevailing in the group. They usually melt away when asked to provide evidence, citing 'bullying'. Often extremely smug and rather stupid.
A parachutist landed in our FB group today to 'educate' us all about how we are wrong about absolutely everything, ever.
An individual that believes what he or she hears without confirming any facts.
President Trump was able to manipulate his base with repeating a lie, his followers became devoted Parachutist-less Cliff Jumpers.