Do you think that one ought to always seek advice from total strangers in order to be safeguarded from his/her own biases?

Total strangers are, of course, going to have their own biases, e.g. the availability heuristic. They also may not be domain experts in the relevant domains.

I think the title of your post does not connect very well to its body. Protecting yourself from your own biases is great, but it's hard, and substituting other people's biases is not a solution.