Yes, he had to pay for the fence, so what? What 'right' did these people have to a view of the lake? They enjoyed that view based on the good will of the developer. They never had a right to it. If they want a right to it, it now costs $30K.
Malice, maybe, but the fact is, he owns the land. If there are no restrictions that came with the land preventing his building a fence, then the reason he built it is immaterial. It may be a nuisance that lowers property values, and there may be some legal basis there on which they can act. I don't know.
But the fact remains, he can build a fence on his property to raise the value of it.
Would you propose a law against malice?