Agree with you, but Hanyu's twitter fans aren't the only ones who like to re-score. I see a lot of it on Golden Skate, and for/against many different skaters. I've even seen rescoring aimed at an entire country.
Re-scoring is totally fine. But it must be done with a neutral, informed opinion -- and not one that is invariably clouded by bias, otherwise it's just fluff. If you think that Hanyu should get +5's across the board for every element and his opponents should be getting +2s, then your rescoring isn't so much an assessment as much as deluding yourself in order to make yourself (and others) feel better about the result, and tweaking the math until it suits you.
Judges (in singles especially) rarely give out +5s, and you
have to be critical when scoring every skater, even your fave. If there's a lean in the air, that's a -1 reduction, if there's the slightest skid on the landing, that's also potential a -1 or at the very least you can't call the jump effortless, so they don't get that GOE bullet. If a spin travels you cannot give it a +5. If you watch elements through rose-coloured glasses you'll enjoy your skater more, sure... but you will never be able to assess them objectively. And will thus always be frustrated with the judges who are trying to do so.
Rescoring is so obvious when the analyst looks for places to award points to their faves (like removing a < call the tech specialist made), and heavily deducts a rival (like adding a < calll to a rival's jump that they thought the tech specialist should have called). I mean, yeah, sometimes they're right because the tech panel misses stuff but other times it's pretty obvious the attempts to tip the scales by chipping away at a rival's scores while adding GOE and bumping up PCS for your fave.
I also think PCS is one of the stupidest things you can "re-score" because obviously somebody who has even remote bias towards their fave skater and against their rivals will tip the scales heavily to favour their fave while hammering their opponents. I saw one Twitter user that rescored Nathan Chen's GPF freeskate with 7's, and burst out laughing. I mean, even if you loathe Chen, such an assessment is completely devoid of balanced perspective and disregard for how a sport is measured, and immediately debases the legitimacy of your rescoring. Sure it could be your opinion that Chen UR'ed every jump in the GPF, and you'd be entitled to it - but if your rescoring drops his score by 40 points because of it, then it's not even worth discussing with a person like that.
If Hanyu re-uses his programs for Four Continents, I would hope that the PCS and GOEs are measured with a fresh perspective (after all it's under a new system), and if any "rescoring" does end up happening after at least it's done with a fair lens. But based on his previous scores and prior success with these programs, I doubt certain people will be able to treat these programs as absolutes instead of as relatives to prior performances of them.