Dear Deepa Sharma,
If one of the employees left the company because someone passed a sarcastic comment against him or seniors insult their juniors in front of other team members then it clearly shows that your company has not bothered to give a specific shape to the company's culture.
Immediately, discuss with the top management and find out ways on how to create a culture of respect at the workplace. One of the means is to train ALL the employees on business etiquettes and interpersonal skills. Another means is to conduct a survey on the interpersonal environment in the company.
The seniors must be told emphatically that it is their duty to maintain the motivation of their subordinates and their affronts are demotivating the juniors. Their demotivation could be resulting in more errors by them which, in turn, could be resulting in customer dissatisfaction.
What you have quoted are just two visible cases. Nevertheless, there could be cases where an employee does not leave in a huff but neither gives his/her best. Such employees work only to protect their employment but they do now show any affiliation to the company.
Lastly, please look at your recruitment practices also. Has your company employed low-IQ persons in your company? If yes, then they will continue to commit mistakes and no amount of sarcasm or shouting will reduce errors by them. Find out whether it is a recruitment problem. If yes, then start filling the posts with the persons with higher grasping power.
In one of the companies, there was a problem with the Manager abusing his subordinates. Once an external consultant questioned him on his abusive conducted. He replied bluntly that give me a staff who understands the polite language. If the staff does not work unless I shout or abuse them then what can I do?
The challenge that your company is facing is out of the purview of framing a policy. If policies were to change the behaviour of the employees so easily then the world would have been a far nicer place to live in. Even if you prepare a policy, there could be a change for a temporary period and the things could come back to square after a while.
Thanks and feel free to approach me for the assistance of any kind.
Dinesh Divekar