What is the purpose of playing the bass in the first place? Are you trying to "impress" someone, "bolster" you own ego, demostrate to the world how "great" you are? Or, are you trying to make good music to provide good entertainment and enjoyment to you audience?
This entire discussion of lines vs no-lines always seems to end up with a group of bassists with their noses up in the air over those that prefer lines, spouting all sorts of inane crap about the superiority of their abilities. Some of the ones that prefer lines get all defensive when they've got nothing to be defensive about. And, another group tries to take the middle ground to calm down the no-line snobs and make the lined guys feel good, when they shouldn't have to do anything at all.
Gentlemen, the object of playing an instrument is to provide the best music that "YOU" can. If lines are a crutch, or training wheels as some of you say, then so are the side markers that are placed on the neck of your unlined fretless. In fact, using that line of thinking, so are the side markers on the fretted. In fact, let's take it all the way and say that so are the frets and side markers on a regular six-string guitar. Gee, how about the black keys and white keys on a piano. Let's just make them all the same color, same size and spacing and let the "GREAT" piano players step forth and put the crutch users to shame.
I don't really care whether or not a bass player uses lines or not. It makes no difference. The rule of measurement comes in THE QUALITY OF HIS/HER MUSIC.
Now why don't we all just play and do the best job we can. Learn and do a better job each time we do play. And, if you play fretless, use bare necks, lines, dots, or even color inlays on the neck, whatever you choose to do, and hope that your playing will be judged by your music, not your instrument.