It's not uncommon at all. HOAs don't like rentals in their midst. And HOA members certainly don't like them next door.
That's why you are being harassed.
It's up to your landlord to deal with the HOA. Every lease, everywhere, has an implied covenant of quiet enjoyment. That doesn't just apply to noise. It means that a tenant should be able to enjoy the use of his dwelling without interference. It is the obligation of your landlord to make sure of that. If he cannot keep the HOA at bay then HE is in breach of covenant and HE is the one who can be held responsible for compensating you if you are forced to move and incur additional expenses.
I suggest you write to him explaining that to him. Write it on paper, send it by mail with tracking and delivery confirmation and send him a letter every time you get harassed by the HOA, even if you have to send one once a week. You'll need a solid paper trail if you want to throw up your hands and move.
Lesson for the future: NEVER rent a place in an HOA.

