That's news to me.
if you ask all muslim who is their last prophet they will say : Muhammad (pbuh)
if you ask any Shia who their last prophet is they will say Ali (pbuh)
if you ask Khajani's who their last prophet is they will say Mirza Ghulam Ahmad Khajjani
there are about 72 sects in Islam, all created by people from different regions but comes to the same point, there were 144,000 approx prophets who came to earth, the last one is Muhammad (pbuh) and Allah is the sole God.
shia, khajanis, deobandis, koja, they are not believers of Islam, since they dont read the Quraan itself but some other books.
That is remarkably similar to the fashion in which various Christian sects will argue that Catholicism is not Christianity, because "the last prophet" would be the current Pope. I'm simplifying a bit, but it is essentially the same.
As an atheist, I have a somewhat detached view of these ideas. So you won't find me arguing that shia is or is not Islam and the like. I guess I'd view Islam as a very broad phenomena, incorporating many with different ideas - if you wanted my point of view. Anyway, from that perspective, Shia would certainly be included.
This is not very different from saying that the Western world has a "Judeo-Christian" basis. It does not mean any particular sect, just that those broad ideas are at the basis of morality, ethics, justice and permeate popular culture.
Similarly, I do think we could talk about an "Islamic worldview" or an "Islamic culture." But that's just my view, there is certainly no need for you to adopt it.
no no shia is not a sect within islam, it goes very different from the fundamentals of islam. they dont follow the religion at all. they have a different one actually. but yes, i do agree with your point. everybody has their own point of view on various subject.
Tell you what. Since not just you but various others do want to debate "What is Islam", excluding from it various "Not True Islam" here is what I will do. I will use the definition of Islam as asserted by Wikipedia.
This includes Sunni, Shia, Sufism, Ahmadiyya , Non-denominational Muslims, Ibadi, Mahdavia, Quranists, Yazdânism and black Muslim movements.
http://en.wikipedia.org/wiki/Islam#Denominations
Obviously, this does include the various radical violent sects including Al Queda and ISIS. But to distinguish them I will refer to them as "Radical Jihad Muslim/Islam."