Mr. Walalce,
I can only speak for myself, but most "sensitive Belle & Sebastian scenesters" I know are also "energetic, enthusiastic, sincere and [looking] something fresh and (somewhat) original, musically." Additionally, they're not strictly doctrinal people who would refuse to listen to a band because they aren't "indie" enough, they're simply looking for good music wherever it may be found.
I can't believe you'd use adjectives like this to refer to crass fourth-generation pop-punk whores like Fall Out Boy. Have you ever heard this group play live? Quite simply, they're an absolute shit band with no talent and a finely honed sense of how to sell themselves. Nothing wrong with that, there's tons of groups out there with a similar MO, but it just means that they stand at the top of my "most hated popular rock band right now."
I'm not just some "jaded 20-something" shitting on what kids like, there are plenty of other bands that I (again, I can only speak for myself) like and listen to (The Format, Brand New, and Against Me! spring to mind) who primarily appeal to teenagers. There's just no excuse for defending a shit band like Fall Out Boy.
And how dare you compare Pete Wentz to Morrissey. For shame.