I'll preface this by reminding you that I agree that the orange man is bad (though obviously not anywhere near as bad as Bush II) and that I don't want Barrett serving on the supreme super legislature.
H: “Nominating Barrett now will delegitimize democracy!”
B: “Really, why?”
H: “Um, because we strongly oppose her and the dude that nominated her, so we will react badly.”
B: “Ok, so you’re really saying that you are delegitimizing democracy.”
H: "Well, yeah, but it was predictable ahead of time that we would act like this so it's the orange man's fault."
In Rescuing Justice and Equality and a few papers, G. A. Cohen proposes we use the "interpersonal test" to assess whether a purported justification for a policy demonstrates that the policy is fully just or instead merely shows that it is at best a good reaction to others' bad behavior. The way the test works is to take some purported justification, and then imagine whether every member of the community could legitimately offer it.
As an instance where the test fails, imagine a kidnapper has demanded a ransom. Most of us can say, "We should pay the kidnapper because otherwise he won't release the child." But the kidnapper cannot offer that same argument with a straight face--"You should pay me because otherwise I won't release the child." It's not legitimate for the kidnapper to make this claim, and the kidnapper could of course release the child for free.
Something similar applies here. I can say something like, "Trump should not nominate a SC justice right now, because 50% of the population will react very badly to this and become more polarized. They might plot to violate longstanding democrat norms in the future. Some of them will riot." But not everyone can say that with a straight face. The 50% of the population mentioned here cannot say, "Trumps should not nominate a SC justice right now, because we will react very badly to this and become even worse hooligans. We will respond by plotting to violating longstanding democratic norms next time we get the chance. We will relentlessly straw man Barrett and make her out to be a some sort of demon, using sexist language we usually say is forbidden. Some of us will riot if she is confirmed." After all, the people saying this, like the kidnapper, could instead choose to act rightly. We know they won't, but they could, and it's easy for them to do.
Look, why not level with each other? The reality is that there is no procedural norm that says a Supreme Court justice cannot be confirmed this close to an election, and further, there is no norm that says an unpopular president should wait until he is re-elected to nominate someone. Further, we all know--you know it too--that you would oppose anyone Trump might nominate even if he (shudder) is re-elected, as you always do whenever a Republican nominates a justice. You would regard any Republican nominee person as a moral monster, as you always do, and you will succumb to motivated reasoning to convince yourself your accusations are true. We also all know that if the tables were turned and an unpopular Democrat were on the way out, you would think it just and good to push through a new SC justice before the Democrat leaves.
I'm not even saying that to criticize you. I simply want you to admit that you don't really care about or subscribe to these putative procedural norms you invoke, but that instead you care about substance. You recognize the SC is a super legislature and you want your side to win because you think your side is objectively right. There's nothing wrong with thinking that. Just be honest. It's easy.
Indeed, I've noticed that many of my democratic theory friends who constantly extol the justice of democratic procedures, and who refuse to endorse the view that part of what makes democracy just is its tendency to produce substantively correct outcomes, nevertheless don't really believe in democracy. How do I know? Well, whenever they don't get their way and their favorite side loses, they insist that it's because the other side or Putin or some other saboteur undermined the process. It's never because...they lost by the rules. (By the way, congrats to you for not really believing pure proceduralist theories of democracy. All such theories are not merely mistaken, but absurd.)