The phrase "we chill" is generally used in reference to the state of two parties or people being in a state of "chill", "cool" or "non-hostility" towards each other. For example;
Party 1: "Yo, weren't we gonna have that arms race tomorrow?"
Party 2: "I mean, we don't really care much, we chill?"
Party 1: "Sure, we chill."
A person you hate intensely not because they deserve such hatred but because they serve as a focus for your general hatred. A healthy way to dispense with excess animosity.
Jake's not really that big an asshole. He just serves as my hate sink.