Yes, but "quality" is both vague and subjective, not only will different people evaluate aspects of quality differently, different people will legitimately have different views on what components "quality" of a link has. I don't think it's unreasonable to consider the source as a one factor in overall quality (if nothing else as a proxy for things the rater is unable to evaluate about the article in isolation.)
But why should things other than the article directly linked to matter? Why should it be acceptable to downvote an otherwise interesting and correct article just because of the source?
That smacks of voting for ideological correctness over truth or interestingness, a problem that otherwise intelligent people should be able to look past. What makes this site meaningfully different from the front page of Reddit if people will crap on an article because it comes from a source that doesn't align with their politics?
> Why should it be acceptable to downvote an otherwise interesting and correct article just because of the source?
"Correct" is often a probabilistic assessment, not something a potential up/downvoter can determine absolutely.
The source is often an important input to that probabilistic assessment.
> That smacks of voting for ideological correctness over truth or interestingness
Different outlets of the same ideological bent (whether relatively neutral or not) can have wildly different editorial standards which produce wildly different reliability.
I wasn't implying that upvote means agree - only that upvote and agree are positive rather than negative sentiments (because I was proposing a broad pattern match not an exact semantic match). But your explanation does make sense to me, that is a plausible stance, thanks.
I can imagine quite a few sources that I wouldn't want to direct traffic to even if they published something where I agree with the sentiment.