Psalm 108 - My heart is steadfast

We enjoy the beginning of this Psalm, but are all slightly troubled by the Old Testament taunts in the middle. After some fruitful discussion we agree that it's more important to be on God's side than to claim He is on ours.

In particular, the troubling verses are 7-9:

7 God has promised in his holiness:
    “With exultation I will divide up Shechem
    and portion out the Valley of Succoth.
8 Gilead is mine; Manasseh is mine;
    Ephraim is my helmet,
    Judah my scepter.
9 Moab is my washbasin;
    upon Edom I cast my shoe;
    over Philistia I shout in triumph.”

We do come to terms with this passage a bit, but welcome any insights/comments/questions as usual (send them to sabbathschoolfromhome@gmail.com ).