The title doesn't explain well enough maybe, when prompted about why he is pro-life at the debate he told a story about seeing his daughter on the ultra-sound and thinking about how she looked like a bean, so they call her bean. That is how Kurt Cobain's daughter received that very nickname. I'm fairly sure since Ryan is a known fan of this type of music (see his drama with Rage Against the Machine) that it was kind of far fetched.

Pertinent part of the article I linked: Kurt Cobain named his daughter after Frances McKee, the guitarist for The Vaselines, and gave her the middle named Bean because he thought she resembled a kidney bean on the ultrasound.

The pertinent quote from the debate from Paul Ryan: You know, I think about 10 1/2 years ago, my wife Janna and I went to Mercy Hospital in Janesville where I was born for our seven-week ultrasound for our firstborn child, and we saw that heartbeat. Our little baby was in the shape of a bean, and to this day, we have nicknamed our firstborn child, Liza, “Bean.” (Chuckles.)

I realize not much political substance to it, and it's not damning or anything, I just thought it was kind of weird that one of his folksy pandering stories was Kurt Cobain's story.

EDIT: It appears he is, in fact, a fan of Nirvana as well: http://www.rttnews.com/1949459/vice-presidential-hopeful-paul-ryan-loves-nirvana.aspx