Why does it say "Nivlas" and "Basar"?
Malbim: Neveilah is the intact body of the dead. Basar is after it was cut into pieces. They cut the flesh of Chasidim to pieces and cast them to dogs and beasts.
Why are they called "Avadecha" and "Chasidecha"? They were Resha'im - "Shotetu b'Chutzos Yerushalayim... Im Yesh Oseh Mishpat Mevakesh Emunah" (Yirmeyah 5:1)!
Rashi (from Shocher Tov): After they accepted their punishment they are Chasidim. Similarly, "v'Niklah Achicha l'Einecha" (Devarim 25:3) - once he was lashed, he is your brother 1 .
Radak citing his father: There were among them people who served Hashem and His Chasidim. Daniel, Chananyah, Misha'el and Azaryah were among those exiled from Yerushalayim. There were also others, but they were hidden in their houses and could not go out in the streets. Some Chasidim in Yerushalayim were saved from death and were exiled, and some were not saved, based on Hashem's judgment.
Radak: Death atones; once they were killed, they are called "Avadecha".
Sha'arei Teshuvah 4:20: For Chilul Hashem - Teshuvah, Yom Kipur and afflictions suspend, and Misah cleanses. If he was executed and confessed before death, he gets Kaparah from when the fear of death was on him. One who kills him [not based on Beis Din's ruling] spills innocent blood.
Why does it say "l'Chayso Aretz"?
Radak: The Vov is extra. The same applies to "v'Chayso Aretz l'Minah" (Bereishis 1:24), "Bno Tzipor", "Bno Ve'or" (Bamidbar 23:18, 24:3).
