what complicates Bad, i think, is that Bono is fessing up to his own vulnerability and the fact that, were he a person with less going for him, with the ability to let all that go, he could quite possibly have become a user himself -- there's a lot of compassion, and no judgement, for victims of drug abuse. it was also written in specific response to the early-to-mid-80s influx of cheap Pakistani heroin that flooded Ireland and the UK.
i think the song has morphed, especially into Elevation, into Bono's powerlessness to let go of the idea of U2. that's what i took from the Elevation Boston video. that he can't not do what he does, he can't not be on stage in front of 20,000 people, that his drug is U2.
there's a connection, to, i think, between U2 and drugs and even God -- that all are addictions, but all offer glimpses of transcendence, and this correlates beautifully to the middle part of the song, the climax/orgasm of the song where Bono launches off into Bono scat singing, overcome by the power of the music, losing himself and his sense of self as something else takes over. this can happen with drugs, with sex, with music, with religion, with meditation -- it's a specifically ecstatic moment, and it has great power, both healing and harmful. at it's best, it lets us know that there's more than all this, and at it's worst, it draws us into addiction through inbuing us with dissatisfaction with reality. drugs, if used very carefully, can be a shortcut to the insight of the subjectivity of reality, that there is no objective reality, that things exist only because we perceive them to exist. drugs mess with our powers of perception reveling the mundane and everyday to have hidden extraordinariness, but only briefly, and then a toll is taken on the user, especially with a drug as powerful and destructive as heroin.
it really might be their best song, too. at least live.