This song actually does have multiple deep undertones of meaning to it. From what I understand, the whole point of post-rock is being minimalist while at the same time providing as large and elaborate a meaning/message as possible.
I don’t think this song is about the Holocaust at all. Rather, I think it’s about them (the band?) daydreaming about revolution. “Let’s kill first the banker/with his professional demeanour” (obviously) means killing the banker; the epitome of the modern world of capitalism and the guy who’d do anything in the name of profit. “Let's televise and broadcast/the raping of kings” is not to be taken literally. The Kings symbolise the high-end of society that oppress the lesser man. “Let our crowds be fed on/teargas and plate-glass” is about revolt. ‘Our crowds’ refer to the people fighting against established society.
They’re being fed teargas and plate-glass (the “glass” shields that policemen often use when confronting aggressive crowds) by the police and the military. “'Cause a people united/is a wonderful thing” is about how wonderful it is when people with a righteous cause unite.
The rest of the song is about how they’ve gotten too old for revolution and how their beautiful dreams of a better world never came to fruition. “Oh, don't be afraid, though the parade/will not pass our way” means that even though the parade (their parade; all their hopes and dreams) will not appear in their lifetime, it’s still “…nobler to never get paid/than to bank on shit and dismay”. They never succeeded in making the world a better place, but at least they never gave in either. That’s my take on it anyway.
If you want to go further...
'let's televise and broadcast'
The publicity of anti-Semitism.
'the people united is a wonderful thing'
People teaming up on Jews, obviously applicable to the Nazi regime.
'don't be afraid, for the parade
will not pass our way'
Foreshadowing more suffering...
From the band's Wiki page...
"Efrim himself is Jewish, and motifs relating to Judaism are occasionally present in the band's music (he described the band's recording of their first album as a 'Jewish experience')."
'Mount Zion' is in Jerusalem, Israel.
The 'Horah' is a traditional Jewish dance.
'Shoshana' probably refers to Shoshana Parsitz, a famous Zionist activist and Israeli politician.
'Kill first the banker'...Jews in finance/Holocaust.
'Raping of Kings'...I thought perhaps this alludes to Jesus.
'Tear gas'...concentration camp exterminations.
'Plate-glass'...Kristallnacht during the Holocaust.
'It's nobler to never get paid, than to bank on shit and dismay.' Speaking of how the Jews have suffered, but maintain their pride by not asking for sympathy.
These are just a few observations. I'm not sure if the theme/message of the song is supposed to be anything Jewish, or if it's more universal and these are coincidences. But I found it interesting.