Out of all the artists I actually listen to, The Pumpkins might actually have the worst lyrics. It's a toss up between them and The Moody Blues, whose lyrics are awful in a completely different way (and at least in their case, they have beautiful voices to make the shitty pseudo mystic self-help sentiments of the lyrics go down a bit easier). And of course The Beach Boys had their share of embarrassing lyrics but their childlike innocence makes them less offensive.
And oh yeah, I grew up on Corgan's music but he's an enormous douche. I read an interview where he basically came right out and declared that he should be considered one of the greatest musical artists of all time. With a straight face. And he also seemed to specifically hold a grudge re: his status vs. that of Kurt Cobain. It was weird.