You guys must be letting your perspective from reading the books fuck your judgment up. Kirito in the first episode expressed understanding and sympathy to the goals of the crazy, mass murdering game designer. Yes, that's right. The only sense of emotional connection he formed in the first four episodes is with the greatest mass murderer in history. This is your altruistic hero, assclowns.
Why do you think they explored the instant death floor in the first place? Because Kirito, over the course of weeks and months, systematically lied to them about how strong he was, and by extension how strong they were. They assumed (because of Kirito's lies) that they were much stronger than they actually were. If Kirito was never involved with them, they would never have been on the instant death floor getting themselves killed thinking they were strong enough to clear it.