Thunderfoot is a long-time Musk project hater for some reason. That's now his specialty which probably appeals to his audience. There are plenty of equally uninformed youtubers with glowing praise for SpaceX. Just like the real news, people divide themselves into bubbles of whatever reinforces their beliefs.
Provenance kind of matters though because we can't work out all the details of every piece of information and have to put a bit of trust in the source. A way I like it to cite a source with the opposite bias of what you're trying to say. If even the opponents of the general idea agree with some part of it, that's stronger support than it's supporters agreeing.
I very much agree with your comment on an individual level (that of the individual judging the merit of information and opinion they are being presented with). I certainly take provenance into account.
However, I was talking about HN the site. I don't think news websites should (generally) discriminate against sources but the individual readers can (collectively, as with the case of HN and voting) make a judgement call and take provenance into account, including the example you give where an unlikely source makes concessions or gives validity to an argument that they would be usually opposed to.
But the main reason I raised provenance is that the internet has given small individual voices the chance to bring informed insight to the public that previously would have been without a platform. So in this particular case I don't necessarily discount some rando on Youtube making criticisms of SpaceX; they might hold at least some validity. (In this case they obviously didn't.)
