Two books that helped me be more objective (I still struggle with this sometimes ) when researching issues
Intellectual Humility by Ian M Church is a good book for learning how to keep an open mind while still critically evaluating a given issue.
There is also a free online course on intellectual humility by the authors
Ego Is The Enemy by Ryan Holiday - The biggest obstacle to growth is often our own ego. Ego will keep you from even entertaining the idea that you may be wrong about something. Learn to control your ego(which is a lifelong journey) and you will be more willing to challenges your ideas