But the actions of say a parliament are a system with orders of magnitude more complexity and thus we should trust almost no one's intepretation to be unbiased. This is the cursed paradox of history. We so badly want to understand people and societies and it is almost impossible to know we have come to that understanding with any kind of certainty.
Side Rant: This is actually why I see psychology and sociology as dangerous. They often have the rigor of history and cloak themselves in the airs of science.
Really? I remember a fight about a year ago over whether or not it was hot on a particular day in DC. Half the US decided that they couldn't trust the biased weather reporting system. The perception of constant bias in all things meant we couldn't agree on a simple temperature record. A subset of these people cannot trust doctors enough to take vaccines or antibiotics. A further subset cannot even trust that the earth is round.
I know it has been popular, but that is a dangerous line of thinking these days. It is totally fair to say that an analysis of a complex historical event will be tainted by the views of the author(s). But such pieces aren't all history. It is possible to generate bias-free history pieces. For instance, we shouldn't say that every analysis of tree rings or ice cores is bias. That makes it too easy to dismiss a valid representation historical data.
People who see bias everywhere aren't satisfied until they personally test the ice cores. They feel free to deny climate science because everyone with eyes on the cores is biased and untrustworthy. They also see bias in every record of a historical event, again proclaiming them untrustworthy. Since they didn't witness the event and all records are biased, the event either didn't happen or is permanently beyond any accurate understanding. As with ice cores, such people feel free to substitute their own version of history.
It is dangerous to see bias everywhere. Doing so allows us to selectively dismiss anything and everything. We have to agree that there is such a thing as historical truth. To do otherwise is to deny history and all the lessons it has to teach.