1) When they're forced to sit through classes in which teachers present shitty poetry and lie that it is good.
2) When the process of writing poetry is taught badly.
Kids grow up exposed to great poetry. Suzette Haden Elgin once pointed out that "Pattycake, pattycake, baker's man" has a set of stopped consonants in order of articulation from front to back (P, T, K) and the vowels go in the opposite direction. That's fun, and it feels good in the mouth and the ear even if you don't know why. "There's a Wocket in My Pocket" and "Sarah Cynthia Sylvia Stout" are likewise brilliant. They also feature topics that children care about.
I have found that if you show people well-written poems on topics they enjoy, they tend to love those; whereas if you show them bad poems or topics they don't care about, they will be indifferent or hostile to poetry. My strategy for poetic success in a generally poetry-hostile culture is simply to put poems where people are already looking and liking. Public school really does not do that. But look at eurythmy in Waldorf schools -- they're using a mix of music and oratory while kids move around. That's exciting, and the kids love it.
Haiku isn't hard, but in order to teach it well, you have to understand it. Most teachers don't. When I teach haiku ...
* I tell people that writing short things is usually easier than long things, but very short things are a little more challenging again. You can do it, you just have to think more carefully about each word you choose.
* I explain that a haiku is like a snapshot. It's not a story, it's a moment in time. You want to zoom in on something small and examine it very closely.
* It is absolutely okay to count on your fingers when using a syllabic form. I do it. Using your fingers helps you to feel the shape of the poem. Even a haiku, which doesn't have a specific meter, has a certain rhythm. So I'll show people how to do that, and talk about how to adjust the syllables using synonyms and word breaks. How do you make it come out 5-7-5? I can show them that.
* You can talk about why the syllable count is that way, how the Japanese language shapes the form. The most famous haiku by Basho is about a frog jumping in a pond, and that one simple image has been translated dozens of times. Why are there so many? What captivates people about this poem? Which version do students like best, and why? Show a video of a frog jumping in a pond, or go to a pond and look for frogs. Discuss the poem and its versions in that context.
* While the form can be used for any subject, haiku traditionally focuses on nature. Since everyone has encountered things like sky and birds and flowers, it makes for very easy access and a good place to start. It also works with any or all of the senses, which makes it good for inclusive teaching for students with special needs. You can easily find a park or a picture for inspiration, which is also easier than thinking up a poem from scratch. Here's a garden catalog, everyone rip out a page to illustrate your poem. One person might pick a bench with lavender around it, while another grabs a zinnia with a butterfly.
* One thing almost universally left out of Western teaching about haiku is kigo. First, using these helps anchor a haiku in its traditional context. Second, it locks in the timeframe of the poem, which is what it's there for. Third, it encourages students to think about nature in the flow of seasonal changes. Fourth, that opens a discussion about the seasons themselves: what are they in Japan, why did people choose those symbols of the changing seasons, what are the seasons where the students are, and what kigo could they choose to represent those local seasons? A class that first writes a traditional Japanese style haiku, then goes to a park and invents their own kigo for the local environment, is much more likely to understand and enjoy haiku.
If you make poetry come alive, people will love it. If you don't, they won't. It's that simple.