Fair enough. Geremek doesn't need to be 'saved' because he's staging and enacting his protest all by himself, fully aware of whatever consequences. Still, I'd say, there have to be consistent restrictions on when a national government can withdraw a Member of the European Parliament (for instance, only in the case of an indictment under criminal, rather than refusing to sign a pledge of whatever sorts).

The online petition, for what it's worth, states the following:

We, European citizens, are deeply concerned by the principles of democracy and human rights and give our full support to Mr. Bronislaw Geremek. The Polish law of lustration, which threatens him of dismissal from his mandate of Member of European Parliament, directly breaks the rules and values to which Poland solemnly adhered, while becoming a Member State of the European Union.
We firmly urge for the Polish law of lustration to be repealed. Otherwise, we ask our European governments to consider the application of all the provisions of article 7 of the Treaty.

This is pretty much within the vein you suggest.