DB6 is right - a good instructor will start gently. Occasionally I need to be shouted at to get a point home, but I'm probably just thick. I never take his threats of physical violence seriously ....
The worst instructor I ever had wouldn't say boo to a goose, the best one shouts at / swears at / threatens me occasionally, but only when I need it. He's a better pilot than I'll ever be (my opinion), so I listen.
If a strict instructor worries you, how will you cope with flying when you're under other pressure - traffic, crosswinds, and so on?
Ultimately if you're not happy with the instructor, find another one, it's your money. When you find one you "click" with, stick with him/her.