Best used in informal situations or among close acquaintances due to its negative tone. He always tries to do down other people's ideas during meetings.
Pro Tip 2/3
Negative Nuance
Implies unfairness or lack of justification in the criticism. It's not right to do down her efforts when she tried her best.
Pro Tip 3/3
Emotional Impact
Can sound hurtful; consider the listener's feelings when using this phrase. You shouldn't do down your friends, it can damage your relationship.