Why was Valentine so interested in tracking down Professor Mark Hamill at the start of Kingsman: The Secret Service? Did he need him to enact his plan? I thought he was a climatologist, not some neuro-voodoo-guy.
Valentine went around selecting people he felt would be useful in the new world he wanted to create, and if they agreed with him and his plan they'd be implanted with a chip that both blocks the signal and explodes if they leak information before the event, otherwise he'd kidnap them and hold them in his lair until afterwards.
His entire reason for enacting his plan was to save the world from global warming, which he feels is due to humans being likened to a virus, and global warming/climate change is the planet's reaction to us, much like a fever humans get to kill a virus. Given the film states that Professor Arnold is one of the preeminent minds on climate change, naturally Valentine feels he'll be of some use to him in the new world he aims to create.