The subject requires more careful attention than I can offer at this moment. I would commend Prof Hendel's note (if I understand it) that the institution of goel ha-dam balances different values.
I would add two points for now:
1) The text of the Torah implies a more positive view of the goel ha-dam's activity than the actual Halakha. In other words, a person reading the pesukim without Gemara and without halakhic discussion in Rishonim would miss many limitations the Halakha places on the obligation or right to kill the killer. (This is similar but not identical to the way capital crimes are generally treated in torah she-b'ktav and in halakha.
See for example, Enc. talmudit s.v. goel ha-dam.
2) The word "nekama" does not appear in these sections.
