They're already harassing you under the guise of a legal process. A clock punching attorney won't be emotionally invested in the details of a matter, but the victims of such nastygrams are - the main goal of such letters is to make you stressed and worried so you just cave - hence the corollary of hiring a professional who will handle it impersonally

Two wrongs don't make a right, and it certainly may be imprudent to escalate. But there's no moral ground for them to stand on here - they're in the same category as any other spammer. Furthermore nowhere did OP advocate deliberately expanding the scope to their family. If phone calls at inconvenient-to-them times end up bothering their family as well, it's because they didn't do the work to separate their family from their ugly business.

In general I don't buy into the idea of declaring some times as off limits for phone calls, since society has never given me the same courtesy in the early morning. I'd much rather get calls at 10PM than 10AM, and yet it's somehow acceptable for businesses to return an afternoon call at 9AM sharp and pretend they're doing their best to communicate.