Does complimenting a person who commits a haram act—like praising the doer of haram or not condemning them—constitute disbelief?

It is obligatory to avoid obsessive whispering (waswasah), especially concerning matters of disbelief (kufr), because giving in to it leads to great evil. A Muslim must enjoin good and forbid evil according to their capacity, and they are not harmed by people's lack of response if they have fulfilled their duty and clarified the truth. Concealing the truth and abandoning the forbidding of evil is not disbelief (kufr), but rather a sin that incurs a warning, as Allah Almighty says: "And do not mix the truth with falsehood or conceal the truth while you know [it]," and "And [mention, O Muhammad], when Allah took a covenant from those who were given the Scripture, [saying], 'You must make it clear to the people and not conceal it.'" Therefore, abandoning the forbidding of evil and remaining silent about falsehood is not considered disbelief, but rather a sin.