The issue isn't just "supporting Gaza". It's also the necessity to make a clear statement that it is totally, universally unacceptable to deliberately impose hardship on a civilian population because those making the imposition don't like that leadership. That is not negotiable.
Besides which, the objective of such an imposition(that is, to starve the civilian population into rising against said leadership)has never been achieved anywhere in which such tactics have been used.
You don't have to like Hamas to support the flotilla.