How can you say that?!

I do not know how many of you out there have had the chance to experience what I am about to explain in the following post though I have just one thing to say to all of you: never, ever insult a celebrity in front of a new person. The fact that this is in red is representative of the gravity of my suggestion.
Generally , I am someone who is very open and blunt and open when it comes to talking about things. However, in the summer of 2010 I learned the error of my ways:
So, there I was at a lunch with my cousins and my brother, who happened to invite a couple of friends of his for lunch. Initially we were talking about topics which do not concern you or your existence and so, I will not talk about those here. After we were done with lunch I began talking about my distaste for a certain celebrity: Miley Cyrus. Little did I know that the one person who was sitting, silent as an unbroken twig, felt that her an Miley were sisters. I began the discussion by talking about how I disliked her and thought she was a slut. Mind you, my reasons for calling her a slut were not least due to any personal issues with her, nor due to the kinds of songs sung by her. Frankly, I am fond of a couple of songs that she sang and see no reason to be ashamed of my appreciation.
However, I was merely referring to her as a slut due to the influence she has had on 14-15 year old teenage girls who's dresses are fit so tightly that all one could think of, when looking at them, is how ignorant the upcoming generation will be. Anyway, when these words left my mouth, the unnamed girl shot at me faster than a bullet leaves a pistol. She questioned my distaste in the following words: " Who are you to say that ? How can you say that? You have no right to say that!". Might I add, her rage was far greater than her height. I blushed initially and naturally, in order to defend myself, had to say something and so, I asked her another question, the result of which made me feel like I had jumped into a swimming pool bowel first: " Oh my God. Please don't tell me you watch Hannah Montanna". 
She glared at me and then, looked at me with an expression which made her seem similar to a mother who was extremely proud of her son who had graduated from Harvard and said: " Yes. I do and you're just jealous that she's a celebrity and you're not. She IS a good actor. That is why she has her own show".
At this point I did not know what to feel. My options included anger, amusement, insulted or indifference. I questioned myself and wondered if I really did feel jealous of a celebrity who was wearing almost nothing in some of her videos and was influential enough to have an impact on girls who hadn't hit puberty (though their inspired sense of clothing would make them seem like they were the mother of three children, at the very least). In my wonderment I asked her if she related to Miley in any way. (Kindly note that I am merely referring to the said celebrity by her first name as it would be inconvenient and excessive energy would be spent if I typed down the entire name. In contrast, the girl that I had this encounter with seemed to know Miley inside and out and so, felt entitled to call her Miley). She replied back by saying : " No. But you have no right to pass such comments. How would you like it if someone insulted you or made nasty comments about your personality or appearance?".
Hmmm. Though she was right in her own way, seeing as how she was Miley's long lost relative, I told her that whoever said whatever about my personality or appearance would be more than welcome to feel that way and that I was not bothered about any comments regarding these aspects. 
My point is (i) if you have to go to the bathroom, as I did, since I had consumed large amounts of water, do not start an argument of any sort; (ii) if you do, then, be well-prepared for 55 minutes of immense retort, remarks and debates and lastly, never say anything about any celebrity because it seems that they have a large number of relatives who are ready to defend and fight for them, in a manner that might be much greater than the first two World Wars combined.