Ok I'll play the ridiculous game of Morality Olympics here.

On a scale of 10, I'd put the Yassin assassination at a 6.5 because of the collateral damage. I'd give encouraging children to be suicide bombers a 10.

(But I must say that I'd also put being prejudiced against physically handicapped adults, by treating them as if they are a child or developmentally disabled, and incapable of being a leader of a war, at oh, maybe 0.15.)

And I would put assassinating him with a sniper's rifle instead of using a helicopter missile with collateral damage a 4, because that would be standard warfare in a territorial war against a general, which I see as the situation, albeit where one party in the war does not have easy access to rifles, so it still has a rating on the immorality scale. But not because he was physically handicapped! (I do not pity the physically handicapped because I know the vast majority do not want my pity. I do pity children who are taught that to kill themselves is a "good thing," for whatever reason.)

From

Wikipedia's consensus-edited entry:

[....] Yassin opposed the peace process between the Palestinians and the Israelis. He supported armed resistance against Israel, and was very outspoken in his views. He asserted that Palestine is an Islamic land "consecrated for future Muslim generations until Judgment Day" and that no Arab leader had the right to give up any part of this territory.^[13] Yassin's rhetoric did not distinguish between Israelis and Jews, at one point stating that "Reconciliation with the Jews is a crime."^[22] Yassin's inflammatory rhetoric was often scrutinized in the news media.^[23] On one occasion, he opined that Israel "must disappear from the map".^[23] Yassin's declaration that "We chose this road, and will end with martyrdom or victory" later became an oft repeated mantra among Palestinians.^[24]

In 1989, Yassin was arrested by the Israelis and sentenced to life imprisonment. In 1997 Yassin was released from Israeli prison as part of an arrangement with Jordan following the failed assassination attempt of Khaled Mashal, which had been conducted by the Israeli Mossad in Jordan. Yassin was released by Israel in exchange for two Mossad agents who had been arrested by Jordanian authorities,^[13]on the condition that he refrain from continuing to call for suicide bombings against Israel.^[25]

Following his release, Yassin resumed his leadership of Hamas. He immediately resumed his calls for attacks on Israel, using tactics including suicide bombings, thus violating the condition of his release.^[25] He also sought to maintain relations with the Palestinian Authority, believing that a clash between the two groups would be harmful to the interests of the Palestinian people.^[13] Yassin, however, was repeatedly placed under house arrest by the Authority. Each time he was eventually released, often after extended demonstrations by his supporters^{[citation needed]}.[....]

Reem Raiyshi's suicide bombing at the Erez crossing on 14 January 2004, which killed four civilians, was believed by the Israeli military to have been directly ordered by Yassin.^[28] Yassin suggested that the suicide bomber was fulfilling her "obligation" to make jihad,^[29] and Israel's Deputy Defence Minister responded by publicly declaring that Yassin was "marked for death".^[28] Yassin denied having any involvement in the attack's planning.^[28]

[.....]

In his statement Yassin has declared that Hamas did target Israeli civilians, only in direct retaliation for the death of Palestinian civilians. In his thinking this was a necessary tactic to “show the Israelis they could not get away without a price for killing our people.”^[33] [....]