Fifty years ago, the distinguished Israel statesman Abba Eban wrote that “One of the chief tasks of any dialogue with the Gentile world is to prove that the distinction between anti-Semitism and anti-Zionism is not a distinction at all. Anti-Zionism is merely the new anti-Semitism.”
As the examples he gives make crystal clear (e.g., the committed Zionist I.F. Stone), by “anti-Zionism” he means criticism of the policies of the government of Israel and some sympathy for Palestinians.
That principle has become a last-ditch defense of apologists for Israel crimes under the occupation. Any critic, any proponent of Palestinian rights, can be tarred as an anti-Semite. This weapon has recently been wielded to great effect against Jeremy Corbyn in a campaign of vulgar deceit and slander that is shocking even beyond the disgraceful norm.
It would not be surprising if DiEM25 is soon subjected to the same treatment as its success increases and its outreach grows. Be prepared.