Unless the land when purchased has a stipulation (such as many developments have) that states what is and isn't acceptable to keep property values high as part of the agreement, of course you have no right to sue your neighbor. You are free to ignore, plead, beg and boycott your neighbor but not sue them.
Second, you are taking a 1 in a few million and trying to prove the norm. Most people who could afford to buy a home next to a $750,000 home will not purposely lower the value of their home.
"There is no constitutional right to high property value."
True. No argument there.
"Unless the land when purchased has a stipulation..."
Here's the problem with your response: you're arguing the specific here. In other words, it's not about what's legal right now, but whether or not regulating what can be done on one's property *should* be regulated. I can make a strong case that I'm simply doing what I want to do on my own property. You could make an equally strong case that what I'm doing on my property is hurting your economic well being, which hurts your personal liberty. Who's right? How do you know?
Again, this is the problem with libertarianism. Define "liberty". You say that my right to throw my fist stops at your face. But my fist is always going to be further away from my perspective, and your face always closer from yours. There is no such thing as objective 'reason'. Or objective 'fairness'. Or 'equality'.
And that gets me to the second post, where you say that force is the standard to know if rights are being violated. That tells me you're probably a Rand fan. But, if there's no God, and we need an 'objective' answer to what 'reason' or 'freedom' or 'liberty' means, to whom do we appeal? Rand says that two 'rational' people can't disagree, but we're disagreeing right here. And what Rand doesn't tell you is that this statement--"Two rational people cannot have disagreements"--which she repeats often in her works, is *non-negotiable* to her 'philosophy'. Because if two rational people can honestly disagree, then it's not Objectivism, it's Subjectivism, or better yet Nonsensism.
So, on the issue of force, if we can't agree on which version of 'liberty' or 'truth' or whatever should prevail, eventually someone is going to have to come in and pick between competing visions of what these ideas mean. And once we arrive at what 'liberty' means, and you or I still dissent, how do we enforce the decision? Answer: force. Thus, Rand's entire philosophy relies on arbitrary decisions on what abstract concepts mean, which are then backed up by guns. Because if Objectivism isn't backed up by force, how will it prevail? By appealing to God?