What do you think is the ideal way to acquaint managers about their harsh attitude in case of extreme ?

Direct communication is the best way to avoid misinterpretations and misunderstandings. However doing so you have to be prepared to accept or deal with consequences that follow depending on the type and character of a manager you have. Some people accept criticism in regards to their position and take it to improve from it however some find it threatening and in extreme scenarios may want to eliminate that threat. Avoid talking or gossiping with colleagues in matters regarding management or business despite your relationship with them, it creates destruction and may be shared in a very disturbing way.  Approach them but do not tell them their attitude is incorrect because you are not in a position to judge them however tell them what impact their behaviour and attitude is having on you as an individual, refrain from using examples of other people as they may not stand by you in the end.