Also, what the other students of heart-labubu did was wrong. They voiced their opinions after Ace spoke out but got cocky. They are cowards who complain to one another, thinking they are completely in the right without knowing the full context yet do nothing for themselves. They are the truly unjust ones.
And just one more thing. Ace could've easily bought a store-made tart and gotten the same result. He put in that effort to have it refused by rules Riddle couldn't bring himself to break.
Ace cared to learn and was observant enough to address the crowd and not just himself at some point. Ace knows when people abuse a chance or power(intentionally or unintentionally, both from Riddle and the crowd). And Ace is willing to give someone a chance as long as they can reflect on it.
So maybe think of it like this, Ace is the reason Riddle will be able to enjoy himself and the things he likes more.
I get why people think Ace is annoying but he's the only one standing up for Riddle when you think about it. Ace has flaws: downplays the trouble he gets into, says things as they are(which can be seen as unkind in some eyes), and also says things he doesn't mean. But he knows when he fucks up, realizing why Riddle acts the way he does Ace doesn't just let it justify Riddle's tendency to lash out and demand perfection due to trauma. It's self destructive, it's harsh on those around him, it isolated Riddle because he was forcing himself to be what his parents taught him to be.
A lot of people hate Ace, my friend included and for maybe half a year, myself... But without Ace, no body would've pointed out that Riddle was being... Overbearing.
The Queen of Heart had rules, hundreds because her people were utterly insane. These are students who only see someone with insanely high standards and are forced under his tyrannical rule.
Trey knew everything but for years couldn't bring himself to stand against what Riddle thought was right due to feeling guilt that only grew. Chenya saw it too but had no place to say, it just wouldn't hit the same.
Without Ace, Riddle would've been the insufferable one... And dead.