The problem of flag waving is really the least important point but...I am not shocked and horrified that there would be people waving Israeli flags in a European context where there have been joint marches of left organizations and Islamists for Al-Quds day, 'peace' marches featuring Hezbollah flags and open anti-semitism expressed in left media and demonstrations. Keep in mind that at the time when the anti-Germans were most notorious for this symbolism (2001-2004), the covert funding of Hamas was EU policy until 2003 when it was finally exposed (by Ilka Schroeder and others). It is one means by which to question the direction of the left. My appreciation is for what emerges out of the process, the reflection. I am not arguing for us to all go outside and wave the star of David.
As for the black flag, well it has been waved at anti-globalization and anti-war demonstrations since 1998. What has changed? Where are we now? What has been opened up?
More important to me than the questions of flags is why, in a worldwide left characterized by the abandonment of the critique of political economy, embrace of the nation state and therefore national liberation does only one national liberation in history attract so much controversy?
In fact, why is 'Anti-Zionism' a distinct position in itself, one adopted by non-Israelis? Why do the hippy activists in solidarity with Tibet not declare themselves 'anti-Chinese'? Why do people in favor of Kurdish nationalism not declare themselves 'anti-Kemalist'? Why are partisans of the Zapatistas not 'anti-Mexican'?
There has been a shift in discourse that favors the revival of certain nationalisms (Europe, Germany), adjusts the imperialist pole position of others (Iran, Saudi Arabia) and tries to save the 'national interests' of others (American, British), revolving around the judgment of one state in particular. This moment in history I think requires a re-thinking of the focus on Israel, and so far it is only the anti-Germans (for all their flaws, including the previously mentioned odd bit about Poland) and scattered groups like Engage who have addressed this problematic in appreciation for its depth.
I think it's more "withdraw germany's right to exist(ence)", that's a closer translation but not the best.