Knowledge is power.
Manager may get the task accomplished but it actually proves detrimental in long run for the organisation as well as employees. Such tactics are just the most easy one and for the same reason they are adopted by managers, although there are many other ways of getting work done from employees and that requires more effort from manager himself and they don't take that pain.
As time passes not the manager/senior gets exposed to his juniors and lose respect which they otherwise command due to their position.
It is very difficult to avoid your seniors but to cope with such tactics one need to maintain a cordial relationship with colleagues and employees of same level. Competing in a healthy way will pave good growth options for future rather than falling trap to managers wishes. Manager who resort to such tactics will only promote his favorite employee and no other, no matter how much better the other employee performed.
So don't fall in trap of such politics and focus on your work only. If you cannot change the manager you can always change the organisation if you have a good command over your work.
Live before you leave.
He will try to get information about the moments of one officer from another officer. Thus he will be getting all the information about both. Finally, he will be in good books of his top boss. This I have seen in many organisations.
If it comes to workers if all the workers are united they will have an upper hand and management has to act to the tunes of them. So they will promote some selfish worker to start a second union so that there will be always opposition among the workers and the situation will be exploited by the management. This situation will be very good for management.