The key part to recognize is that every position has an inherent bias to it, and just because a particular position happens to be mainstream doesn't make it less biased. Canadian Dimension is on the far left of Canadian politics, however it can be argued that the reason for that is that Canadian political mainstream is biased towards the right.

In general, these labels aren't terribly useful and they're just used to dismiss information without actually engaging with the content. It's much better to point out the cases when reporting is not factual, and to address them specifically regardless of where a source leans politically.

So, if people want to raise disagreements with the content of the article in the submission that's great. However smearing it is just engaging in anti intellectual behavior.