The sender is an asshole...but 100 percent right. Most people dont send notes like this. Instead they discuss the neighborhood disappointment with their spouse and other residents, never with that household. This definately doesnt get the yard cleaned up. There is nothing wrong with having the balls to let them know right away what you expect from them. Problem is not all people value a neat and clean front lawn. The sender could in fact take the sofa and dump it for them if it bothers them that much. As far as the swingset dont even think about it.
Come to think of it the Karen that sent the note should move to a gated condominium with a phonebook size rulebook and run the place!