thank you

I totally understand why you have such an impression. Most of the time, the black sheep look the naughtiest and the bravest, too
In this pics, if you take a look at their stare, they seem too serious, too
but really they're not all that ha ha ha

figuratively, the society sort of tagged people like so as well, "troublemakers, mischievous " when there's so many other adjectives that could positively explain such behaviors really - like adventurous, brave, daring and so on and so forth, but the world has done such a standard conditioning on people that mostly .. just those two words you've mentioned has been used but it's alright because that's probably made life more challenging for the both the black and the white sheep :)