unfair handling of warranty claim

my VW warranty did not want to cover my cars damages because I used the wrong color coolant. Personally I found this was very unfair since I am not a mechanic, I just entered a Engine garage and asked for what the engine light told me to ask for with is engine coolant and using it on the car. Due to this reason firstly I will sell my VW polo gti and will never drive a VW again in my life secondly will preach this gospel of bad treatment by to my 5000 friend on facebook, 3rd I Will make sure that no one I know will drive a vw so long a I live. I regret the day I entered VW to waist my hard earned money.