Lendl wasn't a calm player at all. He argued with line calls just as much as Connors and McEnroe, and was once suspended for exceeding the fine limit.
I have seen the 1985 Canadian Open final between McEnroe and Lendl. It was pretty hilarious how they both took it in turns to berate the umpire and officials, and even sympathized with each other despite hating each other
I'm not sure where this myth of Lendl being a calm, emotionless robot has come from.