How do I confront my parents about this while being respectful?
I know that finding your adult way with parents is a transition that both kids and parents take during life. This is one of those times when you were treated as a kid instead of an adult when you are at adult age.
It is time to speak with them about transitioning with you and seeing you and respecting you as an adult. I think your parents were trying to protect you so you wouldn't be overwhelmed with things as a Freshman. I agree with you though that they should have discussed it with you and come to a decision together.
You can confront them nicely with saying "I know you were trying to watch out for me and take care of me. I love you for caring for me. I would also love if you treat me like the adult that I am. Though I am a young adult, I am an adult and should be consulted with me, about my life. I should be able to have a say in my life. I will respect and listen to what you have to say about things and feel I also deserve and respect the same from you about what I have to say." Then you can bring up how you felt when they went behind your back and you found out what they did.
You can also share how you felt when you lost out on coaching that year. After that ask that they respect your wishes and thoughts on your life and make decisions with you and not just for you. Tell them that it would raise your respect for them if they did so and raise the trust and respect if they consider you as an adult.
Be respectful and pleasant with your discussion but do stand up for your feelings and thoughts. One of the ways an individual can learn to be an adult is to assess an affect of a situation upon another and weigh out the pros and cons of the decisions. You need to be a part of it all or decide on your own so you can learn adult ways and see how decisions effect your life.
I hope this helps with ideas on how to handle this situation.