That ship was carrying humanitarian supplies and was boarded on international waters. The legality of the blockade is highly dubious even if Israel claims it has the right to board ships. How would you react if Hamas declared a similar blockade against Israel? P.S. Those activists expected to get boarded, of course, the idea is to make sure the world doesn't forget about Gaza.
Iraqi Kurdish leader vows to take Sinjar from ISIS (AP)
from the article: Israel Navy intercepts pro-Palestinian activist ship off Gaza coast