I strongly believe that Qadianis /Ahmedis are really confused about the issues of Prophethood and Jesus (a.s.)-second-coming and you can't blame them alone. It's because of all the Hadith which have been pampered by Sunnis and Shias in the name of Islam regarding such beliefs. May be that's why Allah has said so that divisions happen, inspite of the knowledge. (42:14) Which obviously means it happens because of mis-understandings and mis-interpretations.
Shia division started right after the demise of exalted prophet Muhammad (S) because of the similar issues.
I want to know if Prophet Muhammad (S) ever declared anyone Non-Muslim or Kaafir in his life?
Allah ta'la in the Quran openly talks about hypocrites at many places, still He doesn't decalre them Kaafir. We as humans can never know what's in other's hearts. Why should we judge other's faiths? I don't understand it. We do then we commit Shirl in my opinion, because only Allah is the Maliki Yo'middeen, not us! And if we kill some one or do injustice to anyone because of our judgments, then we commit Kufr, too!