Your athletes are a reflection of what you teach and what you allow at practice. If you yell at the ref, they will yell at the ref. If you stomp your feet in disgust, they will emulate that behavior when something doesn't go their way. Speak to the ref with respect and with calmness in your voice. Be encouraging and be classy in victory and defeat. Be the coach you would want your child to have or the coach you would want as a child.