@Antaury
I mean, he's not a tyrant yet.
If you think about it from his perspective, he spent most of his life doing the current emperor's work in order to be the next emperor, even going as far as to arrange a loveless marriage to help him monetarily/politically. But then one day, your dad suddenly announces that you had a brother and he's the crown prince, plus the woman you were going to marry is now in love with him. Not to mention that all of this happens within several months.
Based on the fact that he had a liking to the other prince before they found out he was a prince, I assume he was a normal person until the extreme conditions made him slowly slip into madness and gradually become a tyrant.
So people saying they like the current "tyrant" prince are justified, since he isn't the tyrant just yet, and can still be easily saved (since he doesn't seem to have actually done anything too sketchy yet)