I have been thinking that sometimes personalities of the speaker affects the way I perceive his ideas. i.e. if the speaker has a pleasant personality, and presents his ideas with a calm demur, I will be more agreeable with his point of view and I will take in his evidence with an open mind. However, if the speaker is unpleasant or if he is not calm and confident while presenting his ideas, I sometimes dismiss his ideas and evidence as unworthy of my attention.
I think I might have found a workaround for this issue. Whenever I find myself strongly agreeing or strongly disagreeing with someone's ideas, I would do a "vice-versa" on the speaker's personality and see if I still agree with the evidence. What this means is, if I find myself strongly agreeing with someone, I will imagine him presenting his facts and ideas at the top of his voice or in a very shaky voice. Similarly, if I find myself strongly disagreeing with someone's ideas, I will imagine him talking in a calm manner and in a strong voice.
The idea here is to try and subtract out the effect of personalities when listening to new theories and ideas.