In general, a bad decree from G-d can be overturned through repentance and davening, while a good one can never be revoked. (This is a major theme in the books of Yirmiya and Yonah, among others.)
Yet, when HaShem decreed that the 10 martyrs should be killed, when the angels pleaded in their defense, HaShem said that if anyone says another word, He will destroy the entire world (paraphrased from the piyut in Yom Kippur Mussaf, page 590 in the Artscroll Machzor). Why is this case different? Why wouldn’t HaShem allow their case to be argued, as in other decrees of evil?
Granted we see such responses in cases like HaShem refusing Moshe’s pleas to enter Eretz Yisrael, but at least in those cases it’s a simple “no.” Why here does he not only refuse their pleas but also threatens to destroy the world if they continue?