What if.. having a bias is no better than being closed-minded?
When a person is biased against something or someone, they rely on that bias as their "truth."
So, for example, if someone refuses to hear anything about Christianity or the Bible because they don't want to be told what to do, they are placing their bias above knowledge. Above finding out if there is anything worth knowing outside their bias that could be important or necessary.
So, yes, if you have a bias you can be very closed-minded. But, in the end, all you have is a bias.