Everything is partisan, a lot of it is hacky. what are you trying to say?
edit: wait, are you asking for proof that a self identified hack website is a hack website? I mean, most other places hide it a little bit. Like, snopes you generally have to post some of their rediculous fact checkers to show it.
But, yeah, most fact checkers have shown themselves to be liars. The default assumption of a fact check website is that its a partisian hackery trying to smuggle in lies and their political narrative as objective fact. It would more be on you to give a reason why its not a disinformation platform.
Which would be a bit hard on something that outright advertises itself as hackery.
Edit edit
Okay, he's a mainstream journalist. Thanks for further clarifying he's someone who should be assumed to be lying awaiting other evidence. The whole point of journalists are to lie. That's the job description. If its a formally trained journalist, then, he's trained to lie in a constant and believable method, making him even more untrustworthy.