This pattern is used to draw a parallel between two things, usually to highlight that if one is considered in a certain light, the other is too. It often carries a negative or critical nuance, like saying 'if X is (bad), then Y is (also bad)' or 'if X can be said to be Y, then Z can be said to be W'. The meaning is 'if A is (like that), then B is (also like that)', but it's not a simple conditional; it's a rhetorical device to compare or connect two negative qualities or situations.

You'll often see it in written or formal speech, and it's a sophisticated N1 pattern. The first part uses が or も + なら, where も can add an inclusive nuance. The second part uses も + noun/な-adj + だ/である. For example, 親が親なら、子も子だ means 'like parent, like child', but with a negative twist: if the parent is bad, the child is bad too. It's not used for positive comparisons; it's almost always negative or critical.

Be careful: the first part is not a real condition. It's a set phrase where なら sets up a parallel, not a cause-effect. So don't think of it as 'if A, then B' in a logical sense.