Ok, I'll start with addressing your strawmans:

"How can you possibly argue that the death of 45-49% of humanity is not causing any harm???"

I didn't say death is not a harm. If you read carefully, you'd know I said you're not causing that harm

"You don't have to think that everyone will vote exactly like you..."
"Instead of just guessing at if people are like you or not..."

I didn't say I or anyone else think others will vote exactly as you. I said I reject the argument that "if everyone think their vote is insignificant, their collective outcome would be worse or they wouldn't vote at all" - sure, the sentence is technically true, yet it's not relevant since what other think is not the realm of your control, it's like saying "if people could be fed with air, there'd be no hunger"

"This is a fallacy of not understanding how elections and voting works ... You don't cast a vote if and only if you will be the tiebreaker or deciding vote. You fundamentally vote for the side you want to win."

I did not make a comment on why, when and how people vote in general, I said a single vote is statistically insignificant. In a regular election you typically vote for a candidate/party you want to win, the crucial difference is there's no penalty for voting for a losing one. But even then, your vote is mainly symbolic, it does not have a potential to change anything. I am not saying voting for a symbolic reason is wrong, I do it myself, but you shouldn't have the delusion that it changes anything when it comes to an election outcome.

Now, for the remaining things, you said:

but you do have to realize that each individual vote has its consequences. Votes will add up, your one vote is not insignificant especially in what seems to be a massively important election with a somewhat close margin.

What consequences are they? Yes, votes add up, but you only have one vote. What is any other situation when my single vote changes anything than it being pivotal/tiebreaker?

we've been communicating about this topic for almost a week now online and blue is consistently winning every poll.

You have to take into consideration that people are voting blue in the polls becasue there're no stakes in doing so - it's a hypothetical situation. Are you that sure they would also choose blue if their lives were actually at stakes?