I mean, can Barca, Real, or any big football club really, talk about integrity?
I love how some fans think they have moral high ground because of "history". History's not a free pass for clubs to act like thugs or cunts, which is basically what any big team's management is doing. They only care about "history" when they can market it in a certain way. If it gets in their way, they don't care about it that much. They love selling brand new jerseys that "pay hommage" to an older version of it. But when "history" means (for example) not having a brand on the shirt, they find a way around it. The whole "Unicef" sponsoring stint was just to prep the field for an actual shirt sponsor ("oooooh but it was Qatar foundation, it's an ONG!"). Beautifully cynical.
I also remember the whole circus around one of Bordeaux's young player (Valentin Vada, who turned out to be crap, but was a huge prospect back then): Bordeaux worked its way around FIFA's rules that prevented recruiting foreign kids under 16 by handing out a "job" to the player's father. Since the father had to move from Argentina to Bordeaux for the job, he brought his kid with him. "Oh, what's that you say Mr Vada? Your son wants to play football? My, we can certainly find him a spot in a small local team called Girondins de Bordeaux!". Sounds familiar ? Yeah, it should, Bordeaux was not the first to try to play that card. Anyways, when Bordeaux tried getting Valentin Vada a license, UEFA and FIFA said no because Bordeaux used a loop-hole. Took them a few years (during which Vada couldn't play any official game, he was only allowed to practice). In the meantime, Vada's agent explicitely said that several big teams (Barca and Chelsea, among a few others) called him to say "if your players comes to our city, we'll get him a license in no-time, don't worry". They were all very confident, because apparently all those rules didn't apply the same way depending on how important your team is (and probably on how much you can pay).
I'm just saying that to point out it's the same thing on different levels for a lot of teams all around the world. In that example, Bordeaux acted crookedly in the first place too. All in all, I don't really see how Barca fans should be allowed to lecture PSG fans, just because their team was created later than them. Just like it bugs me to see PSG pretending to take the high road after taking a dump on FFP for years.