A first life toon doesnt need BB to cap easily. Normal and Casual are specifically to let new players learn, or soloists to run the quest when they cant handle it on a higher dif. BB is for advanced players looking for challenge and faster leveling -- be that vets or TRs. There is absolutely nothing wrong with running a quest you dont know on a lower dif, and any perception as such is purely on the part of the observer. Nothing about BB implies anything of the sort. It implies that you want to step up your game and/or earn more Xp in a shorter amount of time -- which is nothing like the condescending view you depicted.
If it were in any way intended to be that way, then it wouldnt be so easy to pick up your streak again after breaking it; it would take many more elite/hard runs to max the bonus, so as to discourage players from dropping the streak and picking it up again later.
Am I (and for that matter the majority of the server) a coward or an underachiever because I solo Prey on casual, knowing I will get the same reward, whether its casual or elite? Of course not. Might someone feel a sense of accomplishment by soloing it on elite just to retain their BB while farming? Sure, I guess -- but that still does not make the inverse true.