On the issue of using the exact same tactics as Hamas when the chips are down - this has already happened. In the early 1940s when the British were in control of Palestine there were several groups that could only be described modernly as terrorists performing operations in and around Palestine. They performed assassinations and bombings, targeting the groups and individuals they viewed as anti-zionist. Notable operations include the assassination of Lord Moyne (a noted anti-zionist who was part of the British governments efforts to limit Jewish immigration) in 1944 and the bombing of the British HQ in Jerusalem in 1946 (killing 91 people).
http://en.wikipedia.org/wiki/King_David_Hotel_bombing
http://en.wikipedia.org/wiki/Walter_Guinness,_1st_Baron_Moyne
There will always be people on both sides of this conflict that are willing to take extreme action to see their side prevail. Usually this is a vocal minority but in the current case we have a Gazan people who are so discouraged and without hope that the majority thinks terrorism is the only viable option. (note: I'm not saying this to defend terrorism - it's still wrong. I'm only saying this in recognition of the fact that lack of viable options is what gets people to turn to terrorism and a peaceful solution will never be found without viable options for the both parties. Of course that raises the question of whether or not viable options actually exist given the extreme and conflicting positions that both parties have laid out... but that's another discussion.)
