You are arguing with someone who is lying to you. You will never "win" this argument or convince them because everything that they say is a lie with a complete different agenda than what they say.
Whether they are a bot or a person, paid or freelance psychopath, they are here to disenfranchise voters and convince young people to throw away their vote on nonsense, or that their vote is essentially meaningless and they shouldn't bother.

I'm not a fan of false dichotomies, but FPTP devolves into a dichotomy

This is just factually false, and it's as simple as looking at the vote results to acknowledge. You can want to present it as a binary, but in reality, voters have many options beyond vote R or vote D.

I don't really know how else to address this for you. Maybe you saw or heard some NPR or wall street journal clip about strategic voting and that was formative for your understanding of how elections work. Regardless, it was wrong because in the real world, when we run real elections, not hypothetical ones, voters choose to do or not do a wide range of different things.

That's not wishful thinking. That's looking at results from real elections. You aren't addressing reality, you are moralizing about how you wish things were, but aren't.

The point is that your moralizing and insistence doesn't have any bearing on how voters actually behave. You have to base your strategy on how things actually are, in the real world, backed up with receipts from real elections.

Strategic voting as strategy is irrelevant if voters don't actually behave that way. You might claim then that American voters are stupid voters who vote against their own their own interests because they don't abide by your approach. Ok fine. Then they are that way. But then you also must acknowledge that your outline if how to win an election is flawed because American voters don't behave that way.

You want voters to vote better but they don't. You want voters to be smarter but they aren't. If you are advocating a strategy that requires voters to be both smarter and better than they are, what's the likelihood of it succeeding?

You can't "fix" voter behavior. You can only adapt the strategies you rely on to accommodate real voters. Advocating strategic voting doesn't do this and lives in the realm of puritanical moralizing.

Sure, Kamala could have made a statement to not support genocide. Maybe she would even have won if she had done so.

That's it. It's all that matters. There was one path to winning the election and it was to get the candidate to change their policy in the most important issue of the election. There was no other path to victory for the Dems.

But at the end of the day, a choice was still made, by each and every American with the option to vote.

We agree that voters don't meet your moral standard. But if you are advocating for strategies that depend on voters being different than they are, its your fault when those strategies fail.

"If Kamala had done this..." - not a personal attack.

Are you Kamala Harris? If you are, Mamala, if I can call you Mamala, why didn't you change your stance on Gaza so that you could win the election?

"If you (which is a plural, by the way) had done this..." - clearly a personal attack.

But please, assume the you was singular. How are those two statements different

I apologize for interpretating the word "you" to mean the word "you". If you mean to speak of "they", you can use language like "voters", or the "electorate", or the "unwashed masses", whatever you prefer. But when you use the word "you" in response to something I say, there is no other way for me to interpret that other than by assuming you are directing the statement at me.

How are those two statements different?

Because one of those is a public figure who's supposed to be representing the will of the people and the other is just some random person.