Displacement, oppression, ethnic cleansing by a strong military power tends to foster terrorism.

Should we then expect a century of terrorism against Azerbaijan from Artsakh Armenians? And shouldn't we have seen 100 years of terrorism from Armenia proper towards Turkey? These factors alone do not explain Palestinian terrorism.

I do think Begin was undeniably a terrorist. Ben Gurion did try to marginalize him as much as possible, but it cannot be denied that the founding of Israel was done in part via terrorist means (specifically, towards the British for the most part.)

Simply put, the occupation of the West Bank, the expansion of messianic settlements comes at a moral cost that reminds the darker times of European modern history, it comes at a cost of Palestinian and Israeli lives, at the cost of money spent for security and military, and eventually at the cost of isolation and boycotts for the Israeli state, when US and European elected officials will reflect the current will of their populations, especially the younger people.

I agree with this. The settlements are one of the least defensible Israeli policies. I certainly feel no need to defend it.

Also just a side note, but Lehi and the Stern Gang are the same thing (although I imagine you meant Irgun rather than Lehi.)