Let me take a stab at this. As a non American non voter who is interested in the outcome of the election.
There are 3 parties to this discussion: the Harris campaign (Democrats in general), the Gaza issue voter, and the lesser evil voters.
The Gaza issue voters clearly believe a genocide is occuring, sometimes affecting them personally, and funded by their tax dollars. They would like some concessions from the Dems (the only likely party to take any action) and their only bargaining chip is their vote. It is clear to me that, if a large number of Americans felt strongly and this way, action would happen.
The Harris campaign has been non responsive on this issue, trying to tread the thin line, where they not only look powerless politically, but also unwilling to take a moral stand for what is right.
The lesser evil voters are absolutely correct that she is still better than Trump, and in more ways than just Middle east.
What I think all 3 parties need to do:
The lesser evil camp, instead of mocking the hold outs, needs to pressure the Harris campaign to make a change. Maybe even join them! (See the last point)
The Harris campaign, needs to think long and hard about what they stand for, and the implications of the Republican-lite gamble paying off. There needs to be some fear of losing voters who they cannot take for granted as they shift to the right.
Finally the Gaza voters. Its fine to play the game of chicken, keep screaming as loud as you can demanding change, but ultimately (secretly) get to the ballot and vote D.