Probably because due to the nature of the issue even actual unbiased source will likely be perceived as biased. The issue is contentious enough for strong tribes to form on both sides - linking to
any source in that situation means taking a risk of making either of them, or often both, hostile to you.
Moreover, if it's about the situation mentioned earlier this year on HN, it's problematic because of its complexity and gravity. Even with just facts and only facts, the change of the narrative (ie. the order you present the facts in) is enough for the same reasonable person to come to opposite conclusions. And that's before accounting for rhetorical devices that aim to manipulate the reader while still not crossing the line and sticking to facts - happily employed by both sides of the discussion in staggering quantities. (Then, of course, there's the other 90% of sources full of lies and fabrications, but let's leave those alone on HN at least...)
In short - it's not worth the hassle unless you're invested in the matter enough to care a lot, and once you are, odds are you won't post an unbiased source anyway. You'll need to do your own research, wade through a metric crapton of some of the worst humanity has to offer, and form your own opinion based on that. I don't think there's a shortcut here.