I would have said it differently, but in the end it comes down to this: you are not the band director.
I have 5 grown kids and what I'm going to say now is going to come off fatherly, but it's what I would have said to them in this same situation:
There will always be someone telling you what to do. Choose your battles wisely, but make SURE somewhere along the way you learn how to do what you are asked without grumbling. That is an important life skill and those who never learn it limit themselves in ways they don't understand.
Ahh, America-land of the sheep!
And here's a free bonus. Your band leader may have some flaws, but everyone does. If I were in your position and music was important to me, I would do EVERYTHING he asked me and PICK his mind for every bit of knowledge he could give. Even if I determined most of what he thought he knew was wrong, I'd ask him to explain his position and then ACCEPT it (at least outwardly). Finally, I would not let a request that I could fill prevent me from playing in my high school band.
If the OP is getting it done on a 6, as he appears to be, then why change it? If the director had a legitimate complaint about the bass (tone, for example), then he might have a leg to stand on, but asking him to change the bass because it looks wrong is purely ridiculous.
Whatever you do, have a PURPOSE (and no, trying to hurt him or the band by your absence is not at all what I mean, purpose BENEFITS SOMEbody) and make the decision with full knowledge of its impact. Please, please do not quit because he is a [fill in something stupid]. Sticking now is practice for later... when it will seriously matter. Trust me, you'll be here again.
I imagine the OP has better things to do as a developing musician than waste time in an ensemble where the director listens with his ears more than anything. I'm not saying that he should give up for this reason, necessarily, but considering that there's no money riding on the line for this gig, there's not much incentive to stick it out.