I have no idea what you are saying, if I harm someone through non-coercive means it is still purposeful human action. How are you defining natural forces?
If you harm somebody without violating their property rights through physical invasion of their property, you are in the clear - you are not a criminal, and force cannot be legitimately used against you.
If you harmed a person through violating their property rights, (proportionate) force can be used against you (or your property) to try and restore.
You can't always deal with human behaviour wholesale, i.e. using general principles (a priori)
Society must adopt general principles (aka "laws") to govern human behaviour. You are not really arguing for lack of rules, are you?
I agree with you that the harm caused by non-coersive action may well be greater than that caused by coersive action. However, I still strongly believe in the principle that society ought not sanction the use of force to counter the former. This is not to say that society is helpless. Rather, that non-coersive means should be used to counter non-coersive harm.
Setting aside the question of environmental damage (which, to count as actual damage, must effect somebody's enjoyment of natural resources), and look at the other examples you give.
1. Malicious gossip can never be prohibited. It cannot even be easily defined. Ultimately, a policy that allows the use of force to prohibit some forms of speech will be abused. You can see that most easily with England's current defamation laws, running amok.
2. Performing necrophilia "in public" is only an issue because public spaces are not properly owned. As soon as they become privately owned, the question of prohibiting necrophilia will become a question for the owner of the spaces to decide. I am sure virtually all would prohibit it, without thereby injuring anybody's property rights.
3. Spying using binoculars again begs the question of where the spying takes place. In general, it is up to people to take reasonable measures to protect their privacy. Like drawing curtains across windows visible from other people's property.
Prove it.
Don't be silly. I already agreed no normative assertion can be proven. I assume, for example, that you oppose slavery. Can you "prove" that slavery is wrong?
In saying "only the former can legitimately be countered by force" I am expressing my view (shared, I believe, by most libertarians).
However, in your system ethical systems are given disproportionate representation according to wealth and capital.
Not really. Wealth and capital are themselves the result of free choices people make. Nobody can become wealthy in a free society without enjoying the accumulated property freely given them by their fellow humans.
By buying a loaf of bread, I am effectively saying "in exchange for that bread, I am happy to allow you, the baker, to become the owner of my $1, to do with as you please, since I value the loaf of bread more than I do my ability to do with the $1 as I please.
When you stop and think about how wealthy people become wealthy (in a free society - no cronies allowed) you will see that they are, in effect, acting as "agents" for others.
The conceptual starting point is one of perfect equality. From that point, property accumulates based on countless decisions of members of society, as they freely choose how to express their personal value scales using the property they own.
The problem with democracy is that its members expect to eat the cake and have it too - use their wealth to purchase things, and then still retain residual claim over their wealth (through the political system) to try and use it (again) to express their ethical preferences.
There is no reason to believe it is a better approach than the harm principle.
The harm principle is completely unworkable. Please try to formulate it in a way that doesn't obviously and immediately results in highly non-intuitive conclusions you too would object to.
For one thing, harm can never be quantified. If action X causes harm to person A, and the prohibition of X harms person B, how can anybody tell which harm is greater?
If Susan is courted by both Abe and Bill, and she prefers Abe, her rejection may well cause huge harm to Bill. He is madly and love, and would rather die than be rejected. Susan's preference to Abe is marginal, while Abe is not nearly as bothered. By the harm principle, should we compel Susan to go out with Bill? If not, why not?
Free men are not equal and equal men are not free.
Government is not the solution. Government is the problem.