Urgent!Toyota Avalon Limited Hybrid And Trailering

I purchased a 2013 Toyota Avalon Limited Hybrid on 3/30/2013 trading in a 2005 Toyota Avalon Limited with a trailer hitch used to trailer a light trailer and fishing boat less than 1 mile from my garage to our private lake. At the dealer we even spoke about the Class 1 hitch and its use. Later, I was told that if I installed a hitch I would void the Toyota warantee. I realize that the owners manual indicates that trailering is not recommended. However, it does not address the manufacturers warantee. I contacted the dealer and they were the ones who told me that the warantee would be voided if I installed a hitch.  Why? Why did they not advise me of this before I purchased the vehicle? My trailer has a tongue weight of kess that 100 lb. and the trailer weighs less than 1,500 lbs.  The dealers suggestion was that they would "put me in a non-hybrid Avalon in lieu of my purchased vehicle. However, I would not have traded my 2005 Avalon if I had any idea of this trailering restriction and warantee issue. The owners manual states that Toyota does not recommend towing or a tow hitch but there is no mention of voiding the warantee.  Please advise me ASAP on this matter. I may be reached at