The simple answer is as it always is-- as somebody once said (the Sports Guy? Seinfield? Kafka?) sports fans root for the jersey. Why? Because when the home team wins, the hometown fans are happy. People like to be happy. Why should that be any different here than elsewhere, like say New York, where ex-Idiot Johnny Damon is now cheered? As much as a sports fan here would possibly have issues with the whole steroids thing, Giants fans know by heart this simple equations: Barry hits = the Giants win.
For those, like us, who are conflicted by the whole thing and are deeply troubled by Barry surpassing Hammerin' Hank and the Babe, we are in a quandary: root for sweetness & light, truth, justice and the American Way and all that and be content with a baseball season of losing, or sell our souls to the devil, join the dark side, and hurt America but have a thrill-ride of a winning baseball team. So we choose to root for him to do well. Our souls do come cheap.
But there's another reason for our love, one that comes with having him around for the past thirteen years or so. You know how growing up you had that totally annoying friend who everyone hated but you kind of grew to love because you've known them long enough to see their good side? That's Barry.