Recommending solution dyed nylon has put me at odds with my best referring carpet store often over the years. They push triexta hard. I’m surprised they haven’t stop recommending me by now.
This is a problem that continues to plague our industry: Referrals from carpet stores, furniture stores, and designers are helpful to our businesses. On the other hand, its difficult to keep our mouths shut when it comes to our customers buying any of the "polys", or in the case of rugs, viscose.
In the end, tact is critical, and of course you'll be referring them to buy the preferred fiber from the the people who refer you.
In my opinion, your direct customer is the most important party. Just watch out how you say things when it comes to the "other choices" (a better word, for example, than "garbage") that the stores and designers are enamored with.