Setting a bad example to the children?

Thank you for your lovely thoughtful comments on my returning-to-Nepal quandary, outlined in my last post. While I'm thinking about that - here is another, far less serious, dilemma.

Some years ago we lived in a little house with parking spaces in a courtyard at the front. It was a lovely little house, with lovely neighbours ...

... Except for the couple who lived at the end of the row. Well, they didn't actually live there. They visited some weekends, but much of the time the house stayed empty. Even so they seemed to think that they owned their parking spaces - so if they should turn up and find anyone with visitors had allowed them to park in their space they had a hissy fit.

To be fair, they had a hissy fit at everything. A child in the front garden with a ball was enough to screw their faces up till they looked like dogs' bottoms.

We never knew their names. We knew them as 'the Miseries.' Even when they were here, surrounded by these wonderful Wiltshire Downs, they grumbled. I'm afraid we laughed at them behind their backs, they made themselves look so ridiculous. 

There was a little passageway beside their garden - leading to the back of the row of houses. There was nothing but a little wire fence between the gardens, so it was easy to see the rather bland, pristine arrangement of their little plot.

Now one year we had a surfeit of sunflower seeds ... I can't remember why ... nor whose idea it was to plant them in the Miseries' garden ... though it was easy enough to slink round there at sundown. The planting involved a lot of rather childish giggling and possibly wasn't a great example to my children (who must have been in their early teens at the time). Or was it? Surely it's okay to respond to people who are terminally grumpy by planting sunflowers in their garden?

So - it is vandalism? Or a justifiable response to people who had a serious deficit in the humour department?