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.