A private company cannot violate constitutional rights. Your rights as guaranteed by the constitution guarantee those rights against government interference not against private individuals or companies. So unless the company is an agent of or acting on behalf of a government official or agency, it cannot violate someone's constitutional rights. They may be committing a crime if they are falsely reporting information to law enforcement authorities. They may also be subject to civil liability for libel, slander or malicious prosecution or some other cause of action. You should speak to an attorney in you area about what legal remedies are available.
Your question does not contain sufficient information to allow an attorney to give you meaningful advice. However, there is nothing illegal when a private animal rights organization investigates conduct of a private citizen who has dogs and dog kennels and complains about the treatment of the dogs. Moreover, visits by animal control agencies of the state or federal government are entirely appropriate--especially here where they have not interfered with your ownership of the dogs or taken any of your property. I see no civil rights violation here-----you have to respect the fact that animal rights organizations may have a point of view over proper treatment of animals that differs from your own. It is not harassment if the only thing that happens to you is visits every few months from a government agency such as animal control----they are just doing their job and it hardly interferes with any of your rights. If there is more to this story, then hire legal counsel in your area to review the situation with you.
One further point---our legal system is focussed on providing remedies for actual economic harm. Even if these complaints have upset you, it is hard to see how this has caused you any actual economic harm. Law suits---even civil rights suits---are expensive, and it would be very hard to justify the economic expense of pursuing a claim in this situation.
You do not have any form of constitutional claim against the animal rights group. As noted by the other attorneys, the constitution protects people from the government not private groups. Your best bet is to reach out to the animal rights group and/or the animal control agency, explain the situation and try to improve your relationship with them. Threatening a lawsuit may be counterproductive.
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