I genuinely don’t understand. Shouldn’t we expect bias regardless of their orientation? Conservative, libertarian, liberal, progressive, Marxist - whatever ideology someone has, whether it has a name or not, whether it is coherent or not, it’s going to contain their bias. Not to be too reductive but that’s how human beings work.
“All those people who disagree with me are biased” is also how human beings work.
I guess some people use “bias” that way, but I use it as simply “all people are biased”. Even if they agree with me. Because I am biased, because all people are biased.
If a Marxist blog advocates privatisation then that’s very different than if a neoliberal blog does.
Sure expect bias, but you have to know what direction that bias is in.