Not sure your source for this, but there is a lot of good information here.
The big difference here between Messi's case (and Mascherano's as well) is how they're going after them. I'm not up to speed on some of the people mentioned in that dialogue, but what have you read about any of those cases? Who was prosecuted to this extent? I just did a quick search and apparently Mourinho did have to pay back taxes for seemingly the exact same thing (and he's also apparently lied about other things to avoid paying taxes), but was he ever handed such a sentence? No. And it's not like we're talking a big difference in terms of the sums they failed to pay in taxes and fines. In addition to that, as I already noted about a month ago or so, the Public Prosecutor called for the acquittal of Messi.
As for this Marta Silva Lapuerta, I've read that she is not only a former employee of Real Madrid between 2000 and 2006, but she's also a close friend of Florentino Perez. She also has had other ties which involve politics as the above notes and from what I can surmise has let other cases go as a result. And since somebody mentioned Franco, her father was a Franco Public Works Minister as noted above. Anyway, she is apparently responsible for it going this far despite again the Public Prosecutor calling for Messi's acquittal. Same goes for the Neymar case with the club. This is just like the transfer ban where the Madrid club member was on the disciplinary committee in that instance.
I don't think Messi pays 50% of 200 million every year, but I'd be shocked if he hasn't easily paid more than 100 million in taxes. Anyway, as that notes, Perez surely has underhanded **** all over the place that has nothing to do with football. If you lived in Spain you'd probably have heard this years ago. In fact he had to testify in a corruption case that involved the former Secretary General of the People's Party, a party that this Marta Silva Lapuerta apparently contributed to and had conflicts of interest in the case as a result of her previously employment As for what is to do with football, Perez is clearly behind a lot of **** like this. He's even asked for journalists to be fired because he didn't like what they wrote.
At the end of the day Messi surely didn't pay all the taxes he should have. How much he knew about that can be debated and I'm not convinced he was entirely ignorant (though I doubt he knew the ins and outs of it all or even the extent). However he's clearly not the only person to have done this as the Mourinho incident demonstrates, though he's very clearly been prosecuted differently (as has Mascherano).
I have a mate who is a Professor and who has lived in Barcelona for three decades now and he always calls Spain "a Third World country" because of things like this.
If I had an advice to give to Messi right now would be to change club this summer.
After the devastating loss at the copa aamerica and this, he must feel terrible, and probably lost motivation. A change of scenery with a fresh start would bring him some motivation.
Btw McSorleyStick deserves a McSorley stick to the head with his annoying hatred toward the greatest player to ever play the game.
That's good advice and he should probably take it. No way this sort of double standard would going on in another country where he'd likely end up playing. Of course were he to leave because of this, something that apparently is part of Mascherano's wanting to leave, it would be exactly what they want.