Oh man that's disgusting, it completely disregards peoples property rights and right to privacy, I knew people have had issues with Home Owner Associations in the past but didn't know it was at the point the local government was digging it all up for some. I'll never understand the mentality of "That person has something I don't. I don't like that. They must be wrong. Let's destroy it and fix them." It definitely seems like a culture issue though, as your third link mentions: Victory Gardens cropped up in the UK after World War II (and presumably during...) and I think greenhouses have always been a staple of the British Garden thereafter. Many houses here don't have the front garden to spare so perhaps thats why I've not seen any (many?) stories of others interfering with peoples property, as in the back garden it's a bit more out of sight out of mind.
I think people are against them because they consider them an eyesore. You'd be amazed at some of the rules HOAs come up with just to be busy bodies. Small towns, like HOAs, often come up with some pretty weird rules, once again for the sake of being busy bodies. The fines they generate also incentivize coming up with controlling laws because then they become revenue generators. Myself personally, I find these gardens pretty nifty even though they're not my thing. I will say though, while I don't think I would find something like this as an eyesore, I have seen many front lawns that are just busted up messes and I can understand why HOAs and townships enforce such laws. Seriously, would you want neighbors like this?