First, elimination of Israel is a good thing. Second, please show me the source.

Indeed, "terrorist attacks" have widely been performed by Palestinians and Palestinian liberation groups. Some were aimless, as they were just the spontaneous expression of the hatred of Palestinians towards Zionists. Some were quite purposeful (and it's not just Palestinians doing that, there were plenty of cases of e.g. terrorist attacks of Ukraine on many people in Russia, the most recent one I remember killed a former Ukraine deputy who defected to Russia, and the blowing up of the Crimea bridge may well be considered one) - with the purpose being anything from assassinations (like the assassination of the minister of tourism by PFLP, and I hope you won't claim Israel's government is innocent and shouldn't be targeted), to raising money, to political demands (the Japanese Red Army Faction hijacked some planes for ransom or to make the Japanese government release prisoners, or to make a point by flying one to DPRK), to perhaps the most objectionable purpose - intimidating Israelis to show that this isn't "their" land.

"Terrorist attacks" shouldn't be equated with each other - they should be looked at in the context of who's leading them, what's their purpose and means. If you reject "terrorist attacks", you're often rejecting the only means of partisan combat for heavily overwhelmed forces. Of course indiscriminate attacks on civilians are bad (though if civilians start shooting at you, you're forced to fight anyway), but, depending on the organization leading them, most terrorist attacks aren't that. There's of course also the wider problem that terrorist attacks can't be the only means towards an end, and don't make sense in a lot of cases. Whether Hamas or PFLP perform them is not up to me, I'll just trust that they know their options better than me. I'm not in a position to teach or moralize them.