The only power you have in a representative democracy is your vote. What you are suggesting here is to give all power to those who unequivicoally support "the slaughter".
Policy is defined by what voters favour, and what direction policies they choose to vote for move a country. In a two party system, which the US effectively is, you vote to move the needle - not for an ideal policy. In this case we know that Republicans are more actively supportive of Israel's military actions than Democrats who passively support them. Republicans are in favor of a much stronger hard line foreign policy strategy against Iran, while Democrats are aiming toward diplomatic interactions.
What you have to ask yourself as a one-issue voter, is which direction do you want the country to move in?
The real opportunity to change a party's policy is during house and senate primaries. This is when you vote for candidates who will influence national policy. If a pro-palestinian candidate creates enthusiasm and wins a seat handidly after a strong primary, that in turn influences other seats (Warner and Sanders -> AOC -> The squad).
Voters is all that matters, that is why Universal Sufferage was so important. If you choose to abstain, you aren't "protesting", you are making your vote irrelevant and allowing others to define how the country will be shaped.
When Gen Z realise they are the second most powerful voting block after the boomers, and start using their votes in every single election, then things will start to change. Perhaps drastically. Because at that point political parties will actually care about trying to win their votes.
