This is a great argument, again, but the guy wasn't arguing a point, he was trying to establish a fact.
He said the JF-17 was not FOC as a matter of fact. If it had been a "I don't think the PAF operationalized SD-10 with the JF-17 because X,Y and Z" - then completely fair. Great.
However, when you have footage of the SD-10 apparently being used operationally with the JF-17 and then claiming it is non-operational as a matter of fact, you're going to have to show proof. If you can't, then you should be wise enough to preface what can only be accepted as an opinion as just that, an opinion. Nothing wrong with having an opinion as long as it's well reasoned. But it shouldn't be conflated as fact.
Moreover, one shouldn't tilt themselves to a viewpoint or perspective simply because it agrees with their prior notions - that's confirmation bias (an incredibly common intellectual disease in the Subcontinent, sadly).
Imagine if someone came here also claiming to be a serving PAF guy and started saying, "the JF-17 HMD/S has been secured. PAF is doing an amazing job..." I'm sure you'd hate it if PAF fanbois took that guy as gospel. Well, it works the other way around as well, i.e. with people skeptical of the PAF embracing other skeptics because he or she is skeptic. The only arbiter in this case is fact, and fact requires proof.