What makes you ask that of them? Are you already approaching their point from the opposite angle and want to find out if they've got a bias rather than challenge their point directly?

Are people not allowed to criticise a publication any more without throwing in a token caveat of: "by the way, publications on the other end of the political spectrum do this too, and I equally don't approve of that" to ground their perceived neutrality before someone challenges their argument rather than their motivations?

Yes. What in my concerns with Vox would imply otherwise?

Vox should call itself 'the progressive lens' or something along those lines, it would be more transparent.

And FYI I think the 'left/right' demarcation is far too simplistic for the categorization of the media landscape today particularly as classical ideologies splinter into movements given new trends. The entire world's political landscape has been upended so it'd be nice if we could agree on some new language.