Intentionally fielding players who you feel will score fewer points than players you leave on your bench is every bit as bad as fielding no lineup at all.
Generally speaking, if you have to ask (yourself or anyone else) whether something is "ethical" or not, then you already know damn well that it isn't.
Tanking is chickens**t and bad juju, and if you choose/chose to do so then I wholeheartedly hope it comes back to bite you.
Play to win. This week. Every Week.
Meh. I can see why some people don't like it, but I still don't think it's cheating. Cheating = breaking the rules. No rules are being broken here. I still say this is the equivalent of real NFL teams resting their starters in week 17 when they have the top seed locked up, regardless of whether the outcome has playoff implications for their opponent or anyone else.
Is it chickensh!t to rest your starters? It sounds like you would agree. But it may also be chicken sh!t to call a time out right before the kicker boots a field goal (as we have seen numerous times this year). It may be chickensh!t to have your QB walk away from the line of scrimmage and pretend he is looking to the sideline having a problem with his helmet while the ball is direct-snapped to the RB to throw off the defense (which happened a few times last year).
The point is . . . it's not breaking the rules, and it's being done to help your team gain a competetive advantage. I think it's fair to call it a b*tch move, if that's your opinion, but it ain't cheating. You aren't helping anybody else. You are doing things which you think will help improve your chances of winning. Whether or not it actually will work or bite you in the arse is on you.