Whoever curses Abu Bakr should be whipped, and whoever curses 'A'ishah should be

[ummahboard.com]

Badr ad-Din az-Zirkashi said: "Whoever slanders her is a kafir, because the Qur'an clearly states her innocence."

The scholars based their ruling on the one who slanders 'A'ishah radhiallahu 'anha on the following evidence:

1. The evidence that is derived from the verses in Surat an-Nur that clearly state her innocence. So whoever accuses her after Allah has declared her innocent is rejecting the words of Allah, which is kufr beyond any shadow of a doubt.

more info
http://ummahboard.com/showthread.php?3917-Articles-(Mother-of-the-Faithful)-Ruling-on-One-who-Slanders-%91A-ishah