On Hockey

I know next-to-nothing about hockey, besides what can be observed superficially while channel-surfing.  I know there's a puck, I know there's a penalty called "Icing," although what it means is as much a mystery to me as "Illegal Touching" is in football.  I know, of course, that there's fighting in hockey, but until I saw Kid Dynamite's recent post, I had no idea it was like this.
There was also an all out brawl that left the penalty boxes standing room only, and included the goalies squaring off  (although the goalies are friends, and Carey Price took mercy on Tim Thomas after flinging him to the ground).  The p.a. system blared "Shippin' Up to Boston" during the fight, adding to the insanity inside the TD Garden
Really?!  Fighting is so fundamental to the event that they cue up special music for the occasion?  And at one point, the announcer says "I guess goalies don't have fight straps, huh?"  Fight straps?  I had to Google this.  Turns out, Wikipedia has an entire article on "Fighting in ice hockey," with such section headers as "Causes," "Etiquette," and "Notable promoters."

Some questions and observations:

I never understood the concept of punching anyone in the head when they're wearing a helmet.  This seems to happen in the NFL sometimes, and I always chalk that up to the heat of passion; but I couldn't believe it happens in hockey (see :29 in the video below).  Since fighting is so common, I'd have guessed they'd have that part figured out.  Step One (offense):  get opponent's helmet off.

Conversely, if you play a sport in which helmets are required and fighting is frequent, why are you so bent on getting your own helmet off?  It makes no sense to me, but it seems to be the protocol in this video (see :40).  Step One (defense):  prevent opponent from removing your helmet.

I'm also surprised no one has had their jugular slashed by an errant skate.  I mean, those guys are wearing knives on their feet!  But maybe "kicking" is covered in the "Etiquette" section of the Wikipedia article...I wouldn't know, I couldn't bring myself to read it.