Obadiah 1: Esau/Edom should love his brother Jacob/Israel

 Obadiah must have been written when Judah was invaded by Babylon, thus he should be alive in times of Jeremiah. Edom (descendants of Esau) became glad when Babylon invaded Judah. We read:

10-14
Because of the murderous history compiled
    against your brother Jacob,
You will be looked down on by everyone.
    You’ll lose your place in history.
On that day you stood there and didn’t do anything.
    Strangers took your brother’s army into exile.
Godless foreigners invaded and pillaged Jerusalem.
    You stood there and watched.
    You were as bad as they were.
You shouldn’t have gloated over your brother
    when he was down-and-out.
You shouldn’t have laughed and joked at Judah’s sons
    when they were facedown in the mud.
You shouldn’t have talked so big
    when everything was so bad.
You shouldn’t have taken advantage of my people
    when their lives had fallen apart.
You of all people should not have been amused
    by their troubles, their wrecked nation.
You shouldn’t have taken the shirt off their back
    when they were knocked flat, defenseless.
And you shouldn’t have stood waiting at the outskirts
    and cut off refugees,
And traitorously turned in helpless survivors
    who had lost everything.

Edom is similar to the ones who became glad when the Jews were persecuted and killed by the Nazis. Edom took advantage of this situation. Edom thought of themself as a much more valued people than the Jews that were being despised at that moment. Edom became proud and arrogant. In a similar situation, it is very easy to despise the poor today as if they just have what they deserve (judging that they are lazy, for instance). Even though it may be true, it was also true that the Lord was punishing Judah for their sins but no one should be glad about it.