I don't think this is a knee jerk reaction. I think this is a move for short term political gains without regard for the long term societal costs.

They had decided to extend the life of the reactors just last year. No new risk inherent to their design has been exposed. No new tsunami or earthquake risk in Germany has been exposed.

I agree with the person quote in TFA (despite the fact that his statement may be a political play as well) :

"She just wants to get through the provincial assembly elections," said Social Democrat leader Sigmar Gabriel, accusing her of playing political tactics with people's fears.