Complaining...

So being a coach can be tough.  It can also be extremely rewarding.  I am at the moment feeling very frustrated with coaching.  I don't really "coach" that much.  I am more around to supervise and be present for the athletes.  The problem with this is that I get to hear all of the complaining.  Our team has yet to win a game so the complaints seem to fly throughout practice.
"Why are we doing this?"
"We should be working on something else"
"This is stupid and pointless"
I have heard it all and it is starting to make me sick.  I am tired of having to defend what the other coaches are trying to have the athletes work on.
The root of all of this seems to me to be selfishness.  These athletes want to do what they think they need to do.  They look for any reason to criticize and instead of appreciating what they are doing and having fun they are just waiting for the end of practice or they are goofing off.
It is a lack of charity, a lack of doing what is right for others.  Not all of the athletes complain or criticize.  Is it fair to them to have all their teammates doing just that?
I really want to tell them to either appreciate that they actually get to play the game or just get off the field.
No coach is perfect, no team is perfect.  Why is it so hard to except that?
The culture of the team is so off... I wish I had the knowledge or strength or gumption to change it.