i'm not going to debate with moral relativism within politics
a lot of people like to virtue signal because they think that their politics/ideas makes them 'good people'. however, 'good' is just a point of view, same with 'selfish', and what you consider be selfish, such as holding one's own family/nation closer to their heart, i may consider to be good. this is one of the big reasons that moral relativism is stupid stuff to bring into things like this, because there's never going to be a winner or even a 'right' side at this point
like red spy put it,
What he's trying to say is that Nationalism is putting yourself above others. It's not saying "i want to keep my people safe" it's saying "those who aren't my people don't deserve to be safe." It's entirely centered around helping yourself and refusing to help other people whatsoever because they are not 'you'
I don't necessarily understand what moral relativism means, but i'm sure saying that others don't deserve something as much as your people do is entirely selfish and damaging, especially when your people already have more things than others.
Imagine you have a banana peel on your lawn and your neighbor has ten trash cans that someone dumped all over theirs. Most people would offer to help them automatically, since it benefits you in the sense that you now have a good relationship with that person, and it also benefits them because you just helped them clean up their lawn. Nationalism would be refusing to help because you believe your lawn is superior and want it to stay that way forever, and want their lawn to look bad so you look better. You lose nothing, your neighbor loses a lot. On the flipside, you could help them, lose very little and help them greatly.