I remembered there was an Ode to a Vegetarian Haggis. Googling finds more than one:

Ode To A Vegetarian Haggis

1. Oh vegetarian haggis whit a view
Thou glorious, steaming bag of veggie goo
No one could ever say that you
Dish death to beasts,
Not a single murdered chicken, pig or coo
Taints your braw feasts.

2. But noble pud you must ignore the taunting bores
From meaty Caledonia's shores,
The moaning bloody carnivores
Who think you need
To slaughter sheep in scores
To have good feed.

3. Thy beauteous form can satisfy
The keenest neb or mouth or eye,
Wi' as braw' a meal as ane could buy
Pulse, veg and spice
And ev'n sheep eaters that dare to try
Say Oh it's nice!

4 So stuff the purists and their cries of sin
Let's split this pudding, serve and shovel it in,
And what the hell if it's wee skin
A humble plastic bag is.
Let's drink a toast and we'll begin
The vegetarian haggis.

Tim Dalling January 1993

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Address to a Vegetarian Haggis

Composed for the Scottish Croquet Association Burns Supper on 28 January 2006.

Wee brother o' the puddin' king
Whase praises Rabbie Burns did sing,
Relief an' joy tae us ye bring,
That eat nae meat!
For us ye are the verra thing,
A rich rare treat!

Devourers o' the spud an' neep
Whase heart at offal disnae leap,
Whase flesh sheep's stomachs mak tae creep,
Need na be edgy:
For you, nae need tae kill a sheep;
For why? - Ye're veggie!

We see your innards noo revealed
Whaur Scotland's fertile acres yield
Carrots an' onions frae the field,
Mushrooms an' oats!
Wi' richt guid-will the fork we'll wield
An' stuff our throats!

Fergus McInnes

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There are several others - look at YouTube.