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As Harp and Robin explain in this episode, to tear a strip off someone, is to get very upset at them and to express that emotion in a very harsh and angry way. This could involve yelling or screaming, or just very angry, mean words.
As you can imagine, literally getting a strip torn off you would be a very painful experience. Getting a strip torn off you in the idiomatic sense is often very painful in an emotional way!
Other related idioms we talk about in this episode are
-To chew someone out
-To give someone a piece of your mind