After all, they say, Israel does not know how to defend itself against thousands of humans.
One advocate of the march, Akram Atallah, says, "Israel has prepared itself for all wars, but not the possibility of confronting a flood of human beings."
The implication is that Israel would never kill Gaza civilians who don't pose a threat to life. But they won't say that part out loud.
Also, they forget that Palestinians have tried this before. In 2011, protesters from Lebanon, Syria, Jordan, Egypt, Gaza and the West Bank tried to simultaneously enter Israel on "Nakba Day." A few hundred from Gaza were deterred when Israel fired some rounds towards them; one was reportedly killed. The Lebanese, Egyptian and Jordanian armies actively stopped the marchers from their borders.