Let's look at this situation from a few different angles.
Let's begin with "buyer beware." Are these fake products obtained through reputable channels - or is your 'supply house' somehing like E-bay or Craigs' List? Any vendor providing bad product - for whatever reason - can only suffer if the product is found wanting.
Then there's the matter of -dare I say it- old fashioned horse sense. Remember when folks were proud of their work, and happy to put their names on it? Brands earn their value by performing better than their generic counterparts. I suspect that "Belden" is more respected than "Acme Supply and Distributor" brand cable.
The customer has some role in this as well. Do they really care? Or, do they only care about the cost of installation, not considering other factors (lifetime, reliability, etc). If the customer wants to pay for a Yugo, they ought not expect a Mercedes.
Finally, there's the role of requirements. That is .... can anyone outside a lab tell 'riser' cable from 'plenum?' Or Cat-5 from 5E? The incentive to cheat is particularly strong when the customer can't tell the fake from the real deal.
Add to this the various parties that attempt to manipulate codes (and standards) for their own commercial advantage, and you've got the recipe for fraud.
In some ways, this is a good thing. After all, these fakes do serve the purpose of keeping the 'respectable' guys honest. If you really can't tell the difference between the products, no one will be able to charge a premium.
Now, I am of the opinion that you never come out ahead when dealing with a scoundrel. Some sources of material have, countless times, supplied inadequate or fraudlent products. I submit that anyone who would add poison to pet food and baby formula, in an attempt to manipulate nutrition test results, is someone you don't want to do business with.
Moreover ... when these deadly practices are actively promoted, defended, and participated in by a government, it goes beyond penalizing / shunning a particular firm. A bad tree does not bear good fruit - ever.
Fool me once, shame on you. Fool me twice, shame on me!