1) Asperse 2) Disbelieve 3) Disrepute 4) Expose 5) Humiliation 6) Impeach 7) Invalidate 8) Rebut 9) Shame 10) Shamefulness 11) Smear 12) Smirch 13) Taint 14) Unbelief 1) Cause to be doubted 2) Damage reputation of 3) Damage the reputation of 4) Dishonor 5) Dishonour 6) Disrepute 7) Drag through the mud 8) Engage in a smear campaign 9) Impugn 10) Refuse to accept 11) Reject as false 12) Show to be untrustworthy 13) To give no credence to 
• (v. t.) To refuse credence to; not to accept as true; to disbelieve; as, the report is discredited. • (n.) Hence, some degree of dishonor or disesteem; ill repute; reproach; -- applied to persons or things. • (v. t.) To deprive of credibility; to destroy confidence or trust in; to cause disbelief in the accuracy or authority of. &b...
to make people stop respecting or trusting someone
Dis·cred'it noun [ Confer French discrédit .] 1. The act of discrediting or disbelieving, or the state of being discredited or disbelieved; as, later accounts have brought the story into discredit . 2. Hence, some degree of dishonor or disesteem; ill repute; reproach; --...
refuse to believe 
[v] - damage the reputation of 2. [v] - cause to be distrusted or disbelieved
discredit 1. Loss or want of credit; impaired reputation; disrepute, reproach; an instance of this. 2. Loss or want of belief or confidence; disbelief, distrust. 3. To show to be unworthy of belief; to take away the credibility of; to destroy confidence in. 4. To injure the credit or reputation of; to bring into discredit, disrepute, or loss of est...
disgrace verb damage the reputation of; `This newspaper story discredits the politicians`
to injure the credit or reputation of; defame: an effort to discredit honest politicians. · to show to be undeserving of trust or belief; destroy confidence in: Later research discredited earlier theories. · to give no credence to; disbelieve: There was good reason to discredit the witness.
[ASVAB glossary] reject as false; refuse to accept the state of being held in low esteem