For the sake of being clear, Bernie has criticized Israel very explicitly and has condemned their violence more than the vast majority of US politicians, please don't just take what that random guy said at face value.

Its entirely possible Bernie has a mixed record on Palestine or isn't a perfect representative (I'd need to go look at primary sources and ideally voting records), but the person who left that comment is likely just expressing their anger at feeling like there's not more they can do to help, knowing that innocent lives are being lost

Hopelessness that has turned into bitterness is understandable in the current global political landscape but isn't a good source of credible information

Edit: not gonna go check voting records cause I would have to learn how and barely have the emotional energy to feed myself right now, but here's a quote from sanders' website

“What is happening right now in Gaza is horrendous, it is inhumane, and it is a gross violation of American and international law,”

Here is the page the quote is from, which at a glance explains that as a Jewish American, Bernie is in a unique position to criticize the actions of the Israeli government https://www.sanders.senate.gov/in-the-news/sen-bernie-sanders-has-become-a-leading-critic-of-israels-war-in-gaza/