People don't appreciate being needlessly insulted, I can't fathom that you don't actually understand that. Your "big paragraph explaining a browser" is a strawman. They already say browser, they don't need to elaborate. They can still suggest browsers they do support, the shark just gains them nothing. You honestly think someone seeing the message they have is going to think they are cool/clever/funny/hip? When a course of action gains you nothing and has the possibility of offending potential customers/users the decision seems pretty obvious to me.
I expect most people would not care at all, with the remaining minority either grinning or groaning. I'm not surprised that you think it was ill-advised, but for so many people on HN to be offended or feel insulted because of a lousy attempt at humorously calling out users of out-of-date browsers is just a bizarre concept to me.
