ВЫБИВАТЬ у кого-либо ПОЧВУ ИЗ-ПОД НОГ
[vybivat' pochvu is-pod nog]
To knock the ground from under someone's feet.
To deprive someone of his position or role in society; to undermine someone's confidence in something completely; to disturb someone's peace of mind.
Cf. To cut the ground from under someone's feet; to take the wind out of someone's sails.