Is there a nascent movement to censure Jimmy Carter? Apparently you can sign a "censure Carter" petition here.
I'm not on board, but can't you make the point that what Carter is up to is at least more unusual than the power struggle between Congress and the President on the NSA program? In the one case, you have a disagreement over who has the constitutional authority to determine how war is to be conducted and the borders of the country secured from comunications to and from terrorist operatives in the United States.
As I have blogged without ceasing, there are reasonable arguments on both sides and the matter is an appropriate subject for conversation, not condemnation.
On the other hand, we have an ex-President running around and undermining the policy of the current administration. The issue is not whether the administration can be criticized, but whether it is appropriate for someone to use the status of an ex-President to do so. I can't think of an ex-President who has injected himself into the national and international partisan frey in quite this way.