Catch one on the raw - Idioms by The Free Dictionary
catch (someone) on the raw (redirected from catch one on the raw)
catch (someone) on the raw
To mention a topic that causes one to feel agitated or self-conscious. Primarily heard in UK. I accidentally caught Vanessa on the raw by mentioning her new haircut—apparently, she's really unhappy with it.
catch/touch somebody on the ˈraw (British English) upset somebody by reminding them of something they are particularly sensitive about: She touched him on the raw by criticizing his driving.