Sing me a song, NO NOT THAT ONE!

So i like music, but most people do. And many people who have talked about it have had more profound things to say than what I do.
Some would argue that I don't like music, they would say that i like "noise" (mother) or "anything lacking melody isn't music". But everyone can get fucked. I like my music and y'all are entitled to like yours.
But has anyone else noticed how much people will stand by their favourite bands etc. They love them, they won't hear a word against them, or their favourite genre. They get defensive if you don't like it or say anything bad about it. I mean, if you got a new shirt and i said "your shirt is like someone whacked my retinas with a baseball bat" you'd be offended but you probably wouldn't be like "hell no, that's my favourite shirt, it's so great, the threading is second to none and it's so comfy it's comparable to a bed!" Or something. But if i said "your music is like someone took a dump in my left ear" you'd be all like "nah, fuck you! It's awesome, it's so complex and it's so relaxing, it's like someone's massaging my frontal lobe with their über soft baby hands" Or something. Anyway, you get my point.
Now don't get me wrong. I'm not saying it's bad i'm just saying it's definitely a trend. My best friend and boyfriend, both of whom i love dearly, have the exact opposite taste in music to me. It's not even like they preach it to be awesome or anything but it bugs me when i have to sit there and listen to another chorus of "i got a whole inside and it's 10 miles wide"...yeah ok, i know the lyrics but that's because i was subject to endless drives (which i greatly appreciate) while listening to Escape the Fate on repeat. To be fair they were both pulling their hair out (and my boyfriend even left my house once) while i was busting a rhyme to Dr. Dre. (he might just have been scared away by my dancing.

But WHY?

Now, the only thing i can think of is that it's such a defining part of you, and you put it on the table and when someone says to you "your music is shit" it's like they've said to you "you are a shit person and i think you should be gauged in they rectal area by a baseball bat." I mean, as for the shirt example, I guess it's still a way of showing your personality but you have less invested in it. This is because shirts rarely say anything that you relate to, or you feel is directed specifically at you, which is what many songs/bands do for people. The only reason i can see someone getting equally as offended as when they are wearing their favourite band t-shirt.