Confirmation bias is often, if not completely unintentional. Its not so much as they look at 100 data points and disregard 90 of them (because that's REALLY bad science) its more they have 1000 data points and 975 satisfy the thesis, but about 25 points of data which could arguably be considered outliers if they were both rarer and more unusual disprove the thesis. Note that a thesis is disproved if one statistically significant sample does not agree with the hypothesis, e.g. Coulomb's law would result in a specific force with 1 coulomb of charge. If the force observed is different within a certain amount, and cannot be explained for any other reason, then Coulomb's law would be disproved within those constraints.

Note that limits on measurements and the fact that mathematical models are not perfect (because, alas, the world is not composed entirely of perfect spheres and orders of ten), outliers often exist and are relatively easy to reason away.

Basically, with the concept of the racist: its not so much that he meets one bad minority and reinforces his belief that they are all bad, its that he meets one nice one and ignores his existence as a fluke, and continues to make generalizations.

Also, confirmation bias is not an inherently scientific term, although some silly people define it as that. It is also a very powerful behavioral thing (which is at the root of the scientific problem) and is part of the reason why people will disbelieve scientific evidence that points to homosexuality being static along with other things.