Brian, I admire your work on youtube and other places. And I appreciate your tireless moderating here. However, it seems we are living in a parallel universe. It seems clear to me that a bassist is cutting himself out of a lot of work if he needs his eyes to play to in tune. It surprises me that you don't see that.
It's amazing to me that the idea of playing without using paint as reference is such a controversial topic in the bass community.
I guess we are lucky to be bassists because on every other fretless instrument in the world, we would be in deep trouble if we needed our eyes. I-need-points-of-references-to-play-in-tune is simply not an option on so many instruments.
These things always bring me down because honestly, I feel it reinforces the stereotype of the bassist as someone with less ability than the rest of the band or orchestra. Somehow, in an orchestra of three hundred people, the only person who could not perform written music in tune without his eyes would be the fretless bassist? That doesn't improve our standing in the musical community. I would not want to be the only guy in three hundred to stand up and say "Sorry, I know I was hired to do this but we have to cancel the show because I can't play this music you have given us because I can't read and play in tune at the same time. You know, it's not just me. Most fretless bassists can't play in tune and read at the same time, including some of the greatest bassists of all time". Somehow, I don't think that would heighten our community to the rest of the musicians. It makes us look like idiots. That's why most working bassists don't do this. This make it work. They don't use lines, paint and all that stuff. They make it work. They...use their ears. Billions of musicians have done it throughout time.
Unbelievably, the idea of frets or paint or whatever has been an option for bass oriented musicians for a relatively small time. For countless entire centuries, millions of musicans have played bass oriented instruments without frets or paint. This idea of "I need frets or paint" would not cut it during the 99% of the history of bass oriented instruments.
The real question is: "Did all these millions of musicians play out of tune all this time?". If I listen to many of you here, I'd have to say, yes, I guess they did. I guess we are looking at around 20 centuries of out of tune bass oriented music.
It must have been a major pain to the rest of the dudes in the band, man!
John
You've got quite a few misled notions here. I'll try to break down all that I see.
1. Other fretless instruments
do use references, both visual and tactile, that electric basses do not have. We have a long smooth neck with no tactile reminders or repeatable hand positions that can show the exact placement available on a short neck. What other people do on their instrument over the years has nothing to do with what we do on our instrument. Half of the orchestra doesn't need a bow to make their instrument loud enough to hear when playing stacatto notes- does that mean violinists just need to man up and play pizzicato on stacatto notes? Of course not. Music isn't a contest.
2. You're running with the notion that a bassist who wants to use lines is incapable of playing in tune without them. You're also alluding to the notion that your ears will be less developed when using a lined. These are both false notions. A lined bassist, when not looking at his instrument, is in the same boat as an unlined bassist. You can learn to use your ears on either lined or unlined. The only difference is that a lined can give you an additional reference if you need it. If you're using only your ears and have to correct for wrong notes, which you will eventually have to do, you're no better off than the musician who takes a moment to look down at their instrument to get their bearings. In fact, if they're peeking to get their hand in the right place
before they hit a sour note and have to correct for it, then they're better off than you are. Having additional points of reference simply gives you a better chance of playing in tune.
3. The idea of having visual aids is not at all new. Fretless instrumentalists have been using them when training for centuries. Hell, the whole idea behind frets is to be able to play consistently in tune, and there are gut frets on fretless instruments going back forever. It's not some new issue that electric bassists came up with.
4. You're stating that the rest of the orchestra, band, etc. doesn't look, so it's shameful for the bassist to need to. Simply put- go watch some orchestras. Some jazz bands. People look- all the time. Not necessarily throughout the whole piece, but they still look. It's simply BS to say that no one else is looking so we shouldn't- it's also very easy to disprove. Go watch some videos of great musicians of all instrumental varities. Segovia, Hilary Hahn, John Coltrane, Herbie Hancock, Jaco Pastorius. Countless others. They look. And yet they somehow they haven't all been thrown by the wayside because there's an unwritten rule that good musicians aren't supposed to look.
5. You're not listening to 20 centuries of music played in tune

You've got a little over a hundred years of music to base your ideas off of, and how few of those fretless instruments play as an electric bassist is expected to. In tune immediately without sliding into tune, little to no vibrato, no orchestra to blend inconsistencies in with. There's in fact very little that is referential with what we do.
6. The idea that most working bassists don't use lines is simply false. Lined basses outsell unlined basses by a very large margin, and they're not just going to newbies while the pros are buying the unlined. Look at the who's who of fretless players, and the majority play lined.
Does that make lined basses better? Of course not. It's just another option and a possible additional tool to use. And making use of that tool by looking neither demeans us nor does it make us different from other musicians.
This whole conversation reminds me of the folks who say you're not a real musician if you can't read music or sight read. You can see these folks posting like this all day long here. Meanwhile, Paul McCartney and Stevie Wonder are off making beautiful music despite what they say....