Via NRO, someone didn’t get the memo that liberals are still in “pretend the motive is unclear” phase, the most fun part of which is spitballing about Tamerlan Tsarnaev possibly having brain damage from boxing. Could that be it? Could it be that Bin Laden liked to spar for fun too and finally took one right hand to the face too many circa 2001? What about poor Dzhokhar’s “Holden Caulfield-like adolescent alienation,” a hormone-fueled vortex that had him alternating between cooing over how hot Miss USA is and planting bombs next to eight-year-olds? Will we ever know the answer?

When even Andrew Sullivan can’t resist goofing on lefty theories pointing everywhere except at the obvious, you know this debate is more or less over. It’s embarrassing to the culture that an American leader acknowledging the truth warrants some special recognition, but it is what it is: Credit where it’s due here for Biden, even if the term “knock-off” as a putdown is kind of odd in context. Are “authentic” jihadis, trained overseas and willing to kill themselves for the cause, somehow better? Mind-bending exit quotation about Tamerlan Tsarnaev from his former brother-in-law: “[H]e was angry that the world pictures Islam as a violent religion.”