"Maybe there are good legal arguments why Kagan need not recuse herself..."

"... but there is no good reason that she shouldn't at least come forward and publicly explain her decision."

Not doing so suggests that there is something deeply political (and maybe, like Bush vs. Gore, even something partisan) going on, and that possibility could negatively infect what many of us on the left hope to be Supreme Court affirmation of the constitutional validity of the Affordable Care Act.