2014 GMC Acadia Visibility & Wipers Problems

I HAD JUST PICKED UP 250 PIECES OF CHICKEN FROM GIANT EAGLE TO FEED THE HOMELESS AT THE YWCA AND PLACED THE BOXES IN THE BACK OF MY VEHICLE. AS I DROVE DOWN THE STREET THE WINDOW BEGAN TO FOG SO I TURNED ON THE DEFROST. WITHIN MINUTES OF TURNING ON THE DEFROST, THE WINDOW SHATTERED INTO PIECES. I ENDED UP HAVING TO THROW AWAY OVER 100 PIECES OF CHICKEN, BUT LUCKILY NO ONE WAS HURT. I HAVE CALLED THE DEALERSHIP AND FILED A COMPLAINT WITH THE CORPORATE OFFICE, BUT THEY SAY THEY CANNOT ASSIST. AFTER SPEAKING WITH CANDICE AT GMC, @866-790-3600 EXT 5923331, I WAS TOLD THAT THE EXTENDED WARRANTY I PURCHASED DOES NOT COVER GLASS. I BOUGH THE CAR USED ALMOST A YEAR AGO, PURCHASED THE EXTENDED WARRANTY TO REPLACE THE BUMPER TO BUMPER COVERAGE, SO WHY DOESN'T IT COVER GLASS? WHAT IS EVEN MORE FRIGHTENING TO ME IS HOW DOES A WINDOW JUST SHATTER? THIS IS A DEFECT THAT NEEDS TO BE ADDRESS AND THIS SHOULD BE COVERED BY GMC. I HAVE RESEARCHED AND FOUND THAT THIS HAS HAPPENED IN OTHER GMC VEHICLES AND PERHAPS THIS NEEDS TO BE A CLASS ACTION LAW SUIT BEFORE IT WILL BE PROPERLY ADDRESSED.