Abe Foxman and the ADL are often portrayed as an organization who blacklist anyone that criticizes Israel. Now that's not to say Abe can't be overly defensive on his personal values (i.e. his opposition of Park 51) but there's usually a good reason why an individual or organization are targeted. Unfortunately, some anti-Zionists do (intentionally or unintentionally) engage in anti-Semitism to promote their cause. Popular themes include but are not limited to: well poisoning, tentacles, the Devil, vampires, Nazis, harvesting organs, misquotes from the Talmud and the "New World Order" cabal.
And what is a loaded "anti-Zionist" to do when they get caught? Play the victim card. Ex-Pink Floyd bassist Roger Waters and Helen Thomas would have you believe that there's a conspiracy in the media against people like them. Yet Pat Buchanan and Christine Amanpour (commentators with completely different values) often criticize Israel and are still reputable. I can't help but find the same victim attitude of the loaded "anti-Zionists" in people who claim that Obama "lynched" America.
In short, it's not that you criticize but how you criticize. Please be responsible.