In my opinion buying facebook or the Libra coins will affect bitcoin`s price though, Libra coins will be launched next year, where Bitcoin is crawling, affecting the price of bitcoin which is increasingly expensive, and a there might some investors who will like the LIBRA coin because its new and the bitcoin would be left behind.
I don't think this can affect Bitcoin value because until now Bitcoin still dominates this market and Libra is just a coin issued based on the blockchain platform so there will be no problem. I think Libra will have a lot of legal problems in the United States because it doesn't want this coin to be released but hopes that Facebook can get over it in the near future.