Tomu is such an insufferable hypocrite. He cries, "You cheat but won't let others cheat too," when that is EXACTLY what he has done in multiple other matches. And frankly, when compared to some of the cons that Tomu has pulled in this manga, being able to read the cards because you memorized some details about that particular set feels borderline at worst.
And lest we forget, it's only been three days or less since Tomu was absolute schooled by Shyu Oumei and exposed for his overly analytical way of gambling. It's much too soon for him to be lecturing others and looking down at them for falling into similar traps as himself.