Streetwear has always had a rebellious attitude, but that's because there's always been shit to complain about. Great examples include Supreme's "Fuck Bush" stickers and more recently, FUCT's "Raging Bull" collection which plays on U.S./Mexico immigration tensions. This type of stuff carries on that spirit perfectly: It has a message and uses the clothing to convey it across the collection. But rebelling just for the sake of it comes off as empty and shallow. No one cares if you have a middle finger to the world, but if you're trying to point out how fucked up something is, and want to use your brand to call attention to that, then people are more likely to listen.
2. Have an "anti-" attitude about everything