Fly in the face of

A: I can’t believe John said something so awful.

B: Indeed. His statement flies in the face of everything we stand for!

Note: This idiom means to “be or act in clear opposition to something else.” There is a similar saying, used in American English: “to fly in the teeth of.” Dating back to the 1550s, the idiom’s literal meaning refers to a dog attacking someone by leaping or flying at their face. Very early on, it acquired the figurative sense of verbally attacking someone who disagrees with another person’s opinions.