Trouble from ground distribution block

I have to stick up for Pioneer here. I've never heard of them having problems with noise although anything is possible. 

I have installed several systems with Pioneer HUs and never encountered a single problem of any kind.

I think forbidden is right.  I read about this in the beginner MECP book.

Points where ground can run into a "loop" situation include:

1.  The low-level leads going from the output of a head unit to the input of a crossover or amp.  (Nothing will allow noise to radiate into a system faster than inferior cable with poor shielding.  Always use high quality cables.)

2.  An amplifier or any other component mounted directly to the metal of the vehicle.  (Never mount components to bare metal.  Always try to use an amp rack and insulate the other components from the chasis of the vehicle.)

3.  Grounding several components to chassis ground through their ground lines.  (Some preamp units get their B- connection directly from the interconnect cable - connecting the black wire to ground in this case causes an automatic ground loop.  Ground your preamp components to one point - usually the back of the radio - if their power supply ground is separate from signal ground.

4.  The antenna input.  (The use of antenna ground-breakers that are available on the market today is not a recommended practice, unless there is a severe grounding problem with a particular vehicle.  This ground is essential to the reception of AM.)

Although there are ground-loop adapters available on the market, they are really a "band-aid" approach for a system that should have been wired correctly in the first place.

The simplest way to avoid accessory noise problems is to never share a ground connection with the vehicle's accessory ground path, such as a fan motor or brake light ground.  It is highly likely that a pop or a buzz will be heard in the system whenever the fan is turned on or the brakes are applied.

Plan, Research, Do