Dorian at Postmodern Barney nicely summarizes why killing Northstar is a bad idea:
“You see, I’m sure that Marvel thinks that by killing the most prominent gay character in the Marvel Universe that they’ve actually done something shocking and worthy of comment, but the fact of the matter is that all they’ve really managed to do is demonstrate how creatively bankrupt they are.”
Fanboy Rampage links to Mark Millar’s musings on the event, where he misrepresents the character’s profile (“but he’s a big part of X-Men history and was probably the most high-profile X-Man during the nineties when he was outed in the mainstream media”) to give the event anything approaching heft (and retroactively justify the “and a major X-Man dies” hype). He also boasts about how down with the gays he is:
“As someone who’s won two gay and lesbian awards for the treatment of Apollo and The Midnighter, had glowing reviews in a clutch of gay magazines, was all over the British tabloid press three years ago defending my use of gay superheroes (even when the cardinal of my own church described it as a disgrace) and introduced a gay Colossus into Ultimate X-Men, it just seems preposterous to assume this is bigoted in any way.”
The fallacy of “I’ve never written anything with anti-gay content before, so I certainly must not be now” aside, I actually don’t see any homophobia in Millar’s choice of victim. He needed a warm body of a certain stature (but not of sufficient stature as to make his or her absence in any way inconvenient to the X-line) that he could turn into a cold body. And while that’s cynical and plot-driven, it isn’t homophobic.
Now, Marvel considering the character disposable, in spite of his iconic status? That’s a whole different kettle of fish, but I’ll just point you again to Dorian’s remarks. He puts it better than I would.