The Ghostfacers were chasing a fictional monster because Ed created a creature so Harry wouldn’t leave him. The creature went viral and two psychos decided to become Thinman.
It’s not very often that Sam and Dean actually stumble across human killers, but it does happen from time to time. They kill monsters all the time, but killing a person is much different, but they didn’t have a choice. It can’t be easy to take a person’s life though, regardless of the situation.
I guess Dean was right not to believe in the Thinman lore. He was so sure the guys were idiots that he was convinced it was a ghost. It wasn’t a ghost, but it wasn’t Thinman either. Sam was more open to believing the lore because he was finding it online.
Sam and Dean are still not getting along though. Dean was going to go off and work the case without him. There was an awkward moment when Dean was reminiscing about their childhood when Dean jumped off a roof dressed as superman and Sam jumped off as Batman. Sam thought Batman could fly and ended up breaking his arm. Not that Sam could fly either way, but he was only a kid. Then Dean rode his bike with Sam on the handlebars to the hospital.
Dean has been taking care of Sam since the beginning. If you remember when the yellow eyes demon killed their mother it was Dean who got Sam out of the house. That’s just been Dean’s job for Sam’s entire life. But now it is suddenly a problem.
Check out the preview for the episode on March 18, Crowley is addicted to blood: