You are taking the time out of your day to come to me and train. I want to give you knowledge and skills that you can take with you. Screaming and yelling are not skills that most of us need in our life.
When you are training with me, I look at that as your time you are taking out of your day for yourself. To me I think everyone should do something daily for themselves. It could be a PT session, a Yoga Class, a walk, or even just five minutes alone to sit and breathe.
Whether it is 30 mins or an hour, I want you to get the most out of that time. When you are working with a trainer it may only be 1 or 2 sessions a week, in the grand scheme of things, this is an extremely short period of time in your week. I want to give you the skills and knowledge so you can then spend the rest of your time getting the most out of the days that you are not with me.
I do not think screaming and yelling is the best use of your time, or mine.