You need to understand the program an accept this when hotel follows the program. In this instance Hotel/Receptionist are correct.

Room upgrade terms are along lines
i)Space available at checkin time
ii)Room for upgrade needs to be available for the whole stay at time of checkin
iii)Ugrade is for room occupied by Elite member
(you can't stay in Deluxe and upgrade the second room you do not occupy)
iv)Strictly speaking by those terms in (ii) hotel does not need upgrade you for remaining nights but nearly all will in my experience.
However as upgrade is still 'Space available' hotel is fully entitled to wait until next days checkin time first, and is fairly normal hotel response, as hotel may still sell those higher rooms especially if not many rooms left.

Regards your perception of rudeness. Different guests have different levels of perception, patience, acceptance, listening skills, annoyance if not getting what they ask immediately, so 50/50 whether you are over-reacting here or if receptionists manor, tone or phrasing was at fault when refusing your request, and asking you to check back next day.