sour grapes

(idiom) when someone says negative things about something because they can’t have it

Example Sentences:

A: Do you like my new car? It’s a Honda Civic.
B: It’s okay.
A: You don’t like it?
B: It’s fine. Whatever.
A: That sounds like sour grapes.

When Marty told Ahmad about his vacation plans to China, Ahmad had sour grapes and told him he didn’t like China.

From the Blogs:

Sour Grapes Griping About the High Line Already Starting

Media:

Similar idioms:

1. keep someone in line
2. on one’s high horse