It may be impossible to completely avoid, but one can try and lay the psychological groundwork to protect (at least to some extent) new thoughts as they are encountered. I found one such mechanism that has been extremely useful to me while taking a philosophy course at DBU some years ago. I'm afraid I've lost the exact phrasing of Dr. Todd Kappelman's admonition, but I came away from the course with this maxim. Deny nothing and accept little, but make a distinction between more and less likely. And so one may proceed to examine and consider a thought or point of view as thoroughly as possible with less interference from our innate bigotry .
Conservative friends, calm yourselves. This in no way calls into question the fact that there are real truths and real fallacies. It simply questions our ability to know them at a glance. The maxim is not a call toward the moral amnesty of philosophy so much as a call to humility for the philosopher.