Roman ko Zalim ka salam, good to see you are still alive n'kicking..
so let me give you the same perspective from a different angle, hope this may help you in understanding my point of view.
everyday in every namaz we read.. "ehdinas siratal mustaqeem".. what is this "straight path"?.. Quran translate this as "pray to One God, who is my God and your God and this is the siratalmustaqeem"... till now about 124k prophets have been sent to this human specie (aka ashafulmakhlookaat), the sole purpose of all was not to present something unique or novel but to pull the deviated, morally corrupted and ethically deprived humanity towards one right path. So is the case of this Messiah, at this time of the world, where you see agony and despair everywhere, there are very few who fear God and remember Him, definitely at this chaotic time there is a need of someone if not a Prophet. This is not my theory, there are evidences in all the religions that in the later days there will come a reformer. Imagine if there come a reformer in every faith, each will rise and collide with other.
What did Mirza Ghulam Ahmad brought to the table?.. what he bought is not something new.. its the same old teachings which Holy Prophet had presented some 1400 years ago, despite of the perfect book, the teaching therein are now mere hidden treasure.. the litmus proof is the division of Islam in so many assorted sects... everyone makes his own interpretation according to his/her desires.. number of example are seen everyday for example on this forum... some think jinns are super creatures, some think muta is street legal, some think my god is better than yours, even some think "ya ali maddad" is a very potent nuskha. one book and so many diverse ideologies... do you still think this Un-tainted Book is giving you any benefit? are you teachings still pure? NO, definitely you need someone. And that's why you all are eagerly awaiting for an IMAM MAHDI to remove the dust that has encrusted the Islam for over 1400 years.
Quoting Quran is very easy, just press Ctrl-C and Ctrl-V and viola!.. understanding It is very hard... the very first verses says "hudal-lil-mutaqeen" i.e this book is a guidance for the righteous only, so we must become righteous to unveil its hidden aspects, without that its useless.
So again the only Purpose of Prophets is to revive the humanity and to bring them nearer to God, and that's the take home message from that man you call kafir.
and yes if any Prophet come in our lives, we will accept him, because we follow Quran and thats what it says... " O ye Children of Adam! whenever there come to you messengers from amongst you, rehearsing My signs unto you,- those who are righteous and mend (their lives),- on them shall be no fear nor shall they grieve."....