It is in no way unethical to sit players, unless you are trying to give your opponent extra points to get revenge against another team.
You should always play the lineup that makes sense. To do otherwise would be stupid.
It is usually pretty dumb to not field a complete lineup since percentage stats and negative stats are usually the minority in a fantasy league. In a league with Pts, 3pm, reb, asst, stl, blk, fg%, ft%, and to, you are better off forgetting about TOs, and just trying to accumulate stats. If you have good shooters, great -- you might win the % stats too. If not, sacrifice TOs to get the other stats.
Last time I played fantasy basketball, I was first or second in almost every stat, but dead last in TOs. In fact, TOs weren't even close.