Detach the Faulty Push-Lock Fitting

What happens here

With the air system safely depressurized, the creator proceeds to remove the faulty push-lock fitting. He first pulls out the yellow air line from the fitting, confirming there's no air left in it. Then, using a wrench, he unscrews the brass push-lock fitting from the air tank. He shows the removed fitting, referring to it as the 'source of our problems.'

Goal: Remove the broken push-lock fitting