Example : Paul McCartney said "If Slaughter Houses had glass walls, everyone would be a vegetarian." Now, it also means that everyone who works at a slaughter house is a vegetarian. But, what Paul actually wanted to convey was that slaughter houses are so cruel that you'd feel like quitting non-veg completely. Is there any word for such statements?
I think he is using a hyperbole to convey the image of animals being slaughtered in front you, whose repulsive view would turn you into a vegetarian:
- A figure of speech in which exaggeration is used for emphasis or effect.
- Exaggerated statements or claims not meant to be taken literally.
I think the word you're looking for is metaphor:
A figure of speech in which a word or phrase that ordinarily designates one thing is used to designate another, thus making an implicit comparison.
(Source: American Heritage Dictionary)
I believe the emphasis in the original quote is not on "everyone becoming a vegetarian", but on the glass walls. Which is a metaphor and a vivid image for being able to easily see what happens inside a slaughterhouse.
There is an element of exaggeration here, of course (obviously not everyone would become a vegetarian), but I think it's certainly a stretch to call a hypebole.
The exaggeration of numbers, duration, weight, or similar has to be the clear point of the statement for it to be a hyperbole: I waited for eternity, she weighs a ton, etc.
In the original quote, the main point is the glass wall metaphor of transparency. That's the powerful imagery. That's what drives the point home: glass walls representing something else -- transparency and truth.
When we read the quote, it's not the everyone that captures our imagination, it's the glass walls.
There's a reason why McCartney's documentary is called "Glass Walls" -- http://freefromharm.org/videos/documentaries/meat-org-the-web-site-the-meat-industry-does-not-want-you-to-see/
I would say, hyperbole is a subclass of the answer the OP is seeking. Hyperbolic exaggeration is one way in which a statement might be not really true where the variance from truth is intentional and for the effect of some emphasis. There can be others. Similes and metaphors kind of fall into the category, for instance.
Debating whether that's the best characterization of the example given seems like threadjacking. The original question seems like "is there a more general term for all of these kinds of constructions?"