Bicycle Mechanics - Sailboat casualty with ties to bicycling

So I rented a sailboat today, a Hunter 240 (24 ft) with a buddy of mine. I planned on picking up a friend and his date after a couple hours too. Anyway, we're out in the bay and my buddy at the helm does an accidental tack. In the middle of it as I'm trying to help him recover, there's a loud snap. When we look toward the back of the boat, the rudder is sheared off at the top - at the widest part of the rudder. It's made of fiberglass with a foam and denser fiberglass core. Which later leads me to think:

The rudder is arguably the most important part of a boat. Since a single-point failure of this item is so dangerous, shouldn't it be so overdesigned that it is nearly impossible to break even with slight damage that is not immediately noticeable? Then I started thinking, isn't that how a carbon bicycle fork should be designed as well? I'm not really worried about mine, but some of those things are really light and I wonder how manufacturers mitigate the possible consequences of such a failure. Have any other sailors seen a rudder break like this before?

Luckily we made it back to the marina safely, but then we had to write statements about what happened. The people there thought we might have run aground and that's what broke the rudder (it wasn't). After reviewing our statements, they agreed that it "just broke" and then said that we wouldn't have to pay for it. That gave me the impression that we were responisible for other accidental damage. Isn't that something that their insurance should pay anyway? I never signed a waiver that said I was responsible for accidental damage. It makes me leery of renting there again, but I have no other choice if I want to sail here.

I just wish this had never happened because 1. I feel like I have a bad reputation at the marina, even though they said it's no problem, 2. it shakes my confidence in other fiberglass items (like the whole freaking hull), and 3. I wanted to help my buddy get laid

Actually, one can steer a sail boat using sail trim alone in the case of a rudder failure. I would think that the mast, or the hull/keel junction (on a keel boat) or the centerboard should be the most overdesigned feature of the boat. An accidental tack could put an incredible strain on the rudder, and rudder failures are not that uncommon. I have heard of a few in my 20 years of sailing and racing. Did you round up from being overpowered? To tack accidentally is quite hard as you have to take the nose of the boat through the wind, and a Hunter 240 will not sail that close to the wind anyway. Your buddy must not have been paying much attention to accidentally change course by over 50 degrees or so.

The wind was pretty shifty, and as you probably know once the boat gets close to the wind and loses speed it's easy for the sails to backfill and make it impossible to recover without tacking. So 50 deg is a bit of an overstatement. But he was less experienced than I am and neither of us have sailed this model of boat before.

I think it's great if you can do it, but trying to steer back to the marina with a 300-yd wide entrance and then land using the sails alone is more than I'm willing to try. It wasn't too bad using the outboard, but in my own boat (inboard diesel) I would have been screwed. But my boat has a steel rudder.