AC 9013 - deceit and hypocrisy are very bad things

AC 9013
. . . from the signification of "deceit,"
as being malice from the will with forethought or premeditation,
thus from set purpose.
Evils are done either from enmity, or from hatred, or from revenge,
and either with deceit or without it.
But evils done with deceit are the worst,
because deceit is like a poison
which infects and destroys with infernal venom,
for it goes through the whole mind even to its interiors.
The reason is that he who is in deceit meditates evil,
and feeds his understanding with it,
and takes delight in it,
and thus destroys everything therein that belongs to a person,
that is, which belongs to life from the good of faith and of charity.

[4] Deceit is called "hypocrisy"
when there is piety in the mouth, and impiety in the heart;
or when there is charity in the mouth, but hatred in the heart;
or when there is innocence in the face and gesture,
but cruelty in the soul and breast;
consequently when they deceive by a show of innocence, charity, and piety.