I feel like there was a bit of a leap from a simple question about overnight anchoring to an assumption that there would be inappropriate discharges. Decades ago, when fewer boats had holding tanks, I would have agreed, as did the legislature. In those days, towns (Wolfeboro, Meredith, and the Weirs in particular) encouraged overnight stays at the municipal docks. Good for business, and the boats attracted tourists.
Now, I think everybody is aware of the need to protect our waters and the issue is more one of landowners and boatowners having an appreciation for the desire to use the lakes without harm. The relevant RSA is 270-A.
http://www.gencourt.state.nh.us/rsa/...XXII-270-A.htm
Overnighting on your boat is a little like camping. Maybe a little cramped, hard to get dry on a rainy day, etc, but fun and a family adventure. If you have a friend with a dock, go for it. If you can tie off a bit so you don't bump against the dock, it will feel like you're at anchor.