True
There is a bias (even historical records) and as you say, it is important to know the bias and adjust for it.
Sometimes people (and sources) go out of their way to hide their bias. Personally, I usually like to let people know my bias, right off the bat - and that’s why I say what I do on my Freeper page.
When you find people working very hard to hide what their bias is, you know right away that they’re trying to trick you on something else,