I have no idea how the law works in NC, but having been on the HOA board here, I can relate some ideas that may be applicable.
Most reputable lawyers will give you about 1/2 hour pro bono to discuss your case. Contact the state bar association for recommendations. Also ask about services to help homeowners in your circumstances. The state may also have resources available.
In Oregon, the law pertaining to HOAs is part of ORS Chapter 94 (
http://www.oregonlaws.org/ors/chapter/94). Specifically, the laws mandates that no CC&Rs, by-laws, etc. for a subdivision or HOA may exceed that permitted in ORS.94 but may be more limiting. It may be worth finding out where the NC law is and what is says.
Your local police department may have a neighborhood dispute resolution service. However, if the HOA insists that they are in the right, the resolution service will do no good.
I have a somewhat funny frog story from when my HOA (when still run by the developer) sent me a threatening letter. I had to seek legal advice and pay to have a letter written to the HOA which caused them to go away for good. You may need to go this route. I paid $175 for my letter and it was worth it.
As for ignoring them, it is typical that an HOA has the ability to file a lien on any property within the subdivision. If they file one, they do not have to inform you (at least not here) and neither does the county (where, presumably the lien is filed). You may only discover this when trying to sell and have no time to fight it since it will hold up the sale. Also note that HOAs in most states can add some form of an interest penalty for outstanding fines. Many locales give you the ability to monitor your property record for liens.
and finally, I do believe that if you ask for the justification for their reasoning -- which part of the bylaws, CC&R, state law, etc. -- that supports their claim, then the ball is in their court until they justify their reasoning. Note that they do not have to get a legal opinion, just justify why they are taking the steps that that they are taking (i.e., a reasonable person would agree with them based solely on the justification they provide). If that is the case, then they should not be able to move forward with any fines or other actions until they satisfy your (reasonable) request.
Make sure that all correspondence occurs with registered mail in case a paper trail is necessary down the line.