The Kahan Commission (named after the President of the Israeli Supreme Court) that investigated the massacre in 1983 concluded that “Minister of Defense [Sharon] bears personal responsibility” and should “draw the appropriate personal conclusions arising out of the defects revealed with regard to the manner in which he discharged the duties of his office.” The commission recommended that Prime Minister Menachem Begin remove Sharon from office if he did not resign. Sharon did resign as minister of defense, though he subsequently assumed other cabinet positions. Annexes of the commission report have not yet been made public, and it is not known if they contain additional information specific to Sharon´s involvement.

By all accounts, the perpetrators of this indiscriminate slaughter were members of the Phalange (or Kata´eb, in Arabic) militia, a Lebanese force that was armed by and closely allied to Israel since the outbreak of Lebanon´s civil war in 1975. It must be noted, however, that the killings were carried out in an area under IDF control. An IDF forward command post was situated on the roof of a multi-story building located some 200 meters southwest of the Shatilla camp.

I guess these people can't read either because if it's israels responsibility that sure sounds like israel did it.

Maybe you can send the Human Rights Watch a message to correct them. Be sure to link your wikipedia quote.