Yes, Rejecting one Prophet or Messenger = Rejecting All Prophets & Messengers.
Allah(swt) says in the Qur'an, Surah 26 Verse 123:
'Aad denied the messengers
The interesting note here is that 'Aad were sent only one Messenger Hud(as), while the verse says, they denied the messengers. Thus we understand from this verse that denying one Messenger of Allah(swt) is equal to denying all the other Messengers.
Allah(swt) knows best.