He is definitely in the right, he just doesn't know how to frame it properly right now. The paying off the debt thing just makes Euihyun see him as any other sleazy alpha. If Taejoo could just admit he wants to be the only one then Euihyun probably would have said yes to his just-sleeping-with-him offer but that would require Taejoo to have enough self awareness to realize his own feelings and we know he's not there yet