Sam had the right idea, talking calmly to the kid and figuring out just what is going on, while Dean (Jensen Ackles) decided to charge in guns blazing. As you might expect, that didn't work out great for him. Whatever Jack's (Alexander Calvert) nephilim powers are, they're unlike anything we've seen before. He seems simultaneously all powerful and powerless. He has enough magic inside him to tear a hole in the known universe, but he doesn't seem in control of it at all.
He also had to deal with the confusing prospect of being a young man physically who's only a few hours old in reality. He may have learned English and the basics of being human from his mother while in utero, but he's still pretty lost.
Supernatural seems to be setting up a huge nature-versus-nurture conversation where Jack is concerned. He's the son of Lucifer (Mark Pellegrino), which is a pretty huge clue that he's going to be evil if you argue a person's nature rules their behavior. Dean certainly does. On the other hand, Sam clearly believes Jack is just a lost and confused kid, and if raised with the right beliefs and morals, he could grow up to be a compassionate and harmless person. That's also what Castiel (Misha Collins) believed since he was planning to raise the kid right before his untimely demise.
Regardless of who is right or wrong in this nature-versus-nurture debate, one thing can't be ignored: Jack is dangerous to everyone around him. If he's not lashing out uncontrollably, he's a walking beacon for angel violence. Not to mention, he's eventually going to have Lucifer on his tail if his dad ever gets out of whatever apocalyptic dimension he's in. It's pretty much a given that people around him are going to die.
After realizing this, Dean and Sam make the mature decision to settle their squabble later and take the kid back to the bunker to avoid even more collateral damage.
Eventually though, these guys are going to need a tie-breaker on the Jack situation, and we can only hope that Castiel gets resurrected soon enough to be that third vote. Chuck (Robert Patrick Benedict) may not have answered Dean's pleas to bring Cas back, but we all know he'll return to the land of the living eventually.
Supernatural airs Thursdays at 8/7c on The CW.
(Full Disclosure: TV Guide is owned by CBS, a parent company of The CW)