The trouble with having an open mind, of course, is that people will insist on coming along and trying to put things in it.
Discworld fame Terry Pratchett is one of my favorite authors. Not all his books are equally funny, but some are amazing with insights and humour thoroughly mixed to great effect. "Truth" is by far one of the best I like.
This tongue in cheek remark of his is much more subtle, and very true. It is not an argument against having an open mind but just showing the pitfalls. Nature gives us our genes, but it is nurture (i.e. people around us feeding our open or in-the-process-of-forming minds with their biases and prejudices and likings and theories and what not) that determines our nature. This includes your parents, siblings, teachers, friends, politicians, spiritual gurus, cartoon heroes, sports idols, filmstars and filmstaresses and who ever you care to listen to. That is the reason people who listen more than they speak end up learning more (junk) [people who lurk on sites like maayboli without ever writing, please take note]. That does not of course mean that it is better to be a chatterbox [people insisting on making their opinion on everything known, please take note]. No, definitely not. The middle ground of digesting the sermons is better. One should create a set of filters (a very personal one by selectively choosing only those biases which make personal sense). One should then verify all incoming garbage with existing checks and measures and only separate the useful stuff thereof. If everyone did that, many strifes about such subjects as religions, historical figures etc. will not arise and people will be free to stay in the present and do what is best for themselves as well as for those around them.
One simply cannot help being biased due to the essentially selective "nurturing" one gets, but one should try to ensure that one's biases are very unique.