Imagine if the Lobby in question were for evolution, creation, tobacco, health, free trade, protection, faith, secularity, or anything. If the speaker were a racist, or a sexist, or flat earther, or pro-plagiarist (hey, every profession has its pet hates), using political pressure to make another organization rescind an invitation is just wrong.
In this case, the scholar is Prof. Tony Judt of New York University, who was invited by the Polish consulate in Washington. Judt had been critical of the Israel lobby for suppressing dissent and misdirecting U.S. foreign policy. Here is the Washington Post's account of the dirty deed:
An hour before Judt was to arrive, the Polish Consul General Krzysztof Kasprzyk canceled the talk. He said the Anti-Defamation League and the American Jewish Committee had called and he quickly concluded Judt was too controversial.
If you don't like what someone is going to say, pushing them off the rostrum is wrong.
The cure for bad speech is better speech.