I decided long ago that I like Coca Cola products.
First, I enjoyed the flavor of Coke. That sweet, sweet fizz… Soon I “liked” everything the company produced. I advocated for Coca-Cola products of all varieties, even the ones I didn’t drink!
By extension, I decided I didn’t like Coke’s rivals. I avoided them, to match my new public identity.
Cognitive science has demonstrated that once someone publicly announces a position on a topic, that person rarely changes his mind. Any new evidence or challenge against that believe will backfire, causing the believer to dig in deeper.