That just proves my point-poetry is dumb.

[diamondcutter]

“Poems don’t always have to make sense,” said Ms. Coco. “Sometimes they just paint a word picture.”
What?! Poems don’t have to rhyme and don’t even have to make sense? That just proves my point-poetry is dumb. You could put a bunch of words in any old order and call them a poem.

Source: My Weird School 16 - Ms Coco Is Loco, Dan Gutman

Does “my point-poetry” mean “my point of poetry”?

 

[Phaedrus]

The hyphen is a would-be em-dash. The clause "poetry is dumb" is in nonrestrictive apposition to the noun phrase "my point." "My point" = "poetry is dumb."

 

[Tarheel]

Change the punctuation a bit and you get:

That just proves my point. Poetry is dumb!

Does that help?

 

[Rover_KE]

Or

That just proves my point: poetry is dumb.

 

[emsr2d2]

I'd still go with the original, but with the em-dash and the correct spacing round it (unlike the original).

That just proves my point — poetry is dumb.