They board the vessel, take it to Israel, and then deliver the cargo to Gaza themselves.

They have done that every time, and made it known that was to happen this time."

That just is not true. Any deliveries are only made after the Israelis have removed a whole range of essential items, according to some insane list of what isn't allowed. Medical equipment, building materials - even stuff like jam and various types of sweets. Though I see that they have now offered to allow jam and potato chips and a few items like this into Gaza, having banned them for years...
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It is nonsense to call the behaviour of people resisting an attack by armed intruders "unprovoked violence". If an Israeli boat were boarded in international waters by an armed force of opponents would any sane person describe it as "unprovoked violence" if they laid about the intruders with everything they had to hand?

It would have been more prudent of the protesters to hold off and maintain non-violent discipline in face of the attack - though the history of non-violence, in Israel, as well as in places like India in the time of Gandhi, apartheid South Africa, the Jim Crow American South and elsewhere is that you can still get killed, especially if you are making any progress.