Return to down (idea)

In [Black English], to be [down] with someone is to be [allied] with them, [faithful] to them.

My [homie]s are [down] [with me] so don't arouse my anger [or I will ask them to join me in expressing that anger].
([Gangsta's Paradise])

To be [down] with something is to [accept] it, either grudgingly or completely.

If you're not [down] with that, I got two words for you... SUCK IT.
([Degeneration X])