Because standing up for the truth and against the most corrosive forces of the present global order is a good thing.
And because, notwithstanding the humanitarian work the IHH does, its Turkish members and supporters are Islamists who take an obvious pleasure in drawing Infidel blood and don't deny that they instigated the Gaza flotilla fight. The close ties of IHH to the present Turkish government that is turning that country away from modernity and liberal democracy, and deepening its alliance with the most tyrannical and regressive forces (Iran) in its quest for leadership of the Islamic Umma, in hopes of building another Turkish/Islamic empire, is all the more reason to sign.
(And even because it pisses off all the right people.)
B'nai Brith has proposed... the petition against the Turkish Islamist group that sent armed "martyrs" to attack Israel and die to serve the cause of a death cult and the blood libel of the Jews who, they allege, have no right to defend themselves.
Background on IHH here:
Though my DIIS paper made no mention of IHH's activities in Gaza or in support of suffering Palestinian refugees, some of those angered by the Israeli flotilla raid have instead turned their emotional animus on past critics of IHH, such as myself. While I certainly can't speak with any authority on what took place on the Gaza flotilla boats, I'm rather mystified why the flotilla killings--whether right or wrong--would have any bearing on the factual question of whether the IHH has engaged in illicit financing and episodic support to extremist groups. The evidence in this regard is fairly weighty, and much of it comes directly from the Turkish government -- not the United States, nor the Israelis.and here:
In practice, besides its legitimate humanitarian activities, IHH supports radical Islamic terrorist networks. In recent years it has prominently supported Hamas (through the Union of Good). In addition, the ITIC has reliable information that in the past IHH provided logistical support and funding to global jihad networks.