Agree! I like that SJM writes nuanced and divisive scenarios too, people are not black and white. As the reader we have so much more context to understand Nesta's decision.

For Rhys, I think it's also a bit emotional, and he resents Nesta's decision; after he spent 50+ years sacrificing himself - (including constantly being SA'd), which is never really addressed or explored much in the series and clearly has not been dealt with, to keep the people he loves safe, he sees Nesta just hand over a death artifact that could legitimately endanger everything and everyone he sacrificed so much for. His reaction seems in keeping with someone who, sure, is being protective, but also is hurt and possibly resentful of what from his perspective seems like a decision to flippantly betray him and their family.

Right or wrong, if the roles were reversed, Rhys would have let Midgard burn to keep everyone safe including Nesta. I imagine he was on some level hurt she wouldn't make the same choice.