"Christianity can be taxonomically divided into six main groups: the Church of the East, Oriental Orthodoxy, Eastern Orthodoxy, Roman Catholicism, Protestantism, and Restorationism".
The above are a few words on many factions of Christianity. No faction ridicules other factions and the reality is only Allah knows better who is a true Christian and who is not. Even with these divisions, the Christian world is at the top of industrial and economic developments.
On the contrary, Muslims divide themselves by ridiculing other factions. Let us understand that only Allah knows better. Why the earthly humans should bicker on act like something that they were not given permission to do?
The question is why should it hurt me if someone is a Sunni, Shia, Hanafi, Qadiani or a Ahmadi. Only Allah has the authority to decide who is a good Muslim and who is not. Humans should not take things in their hands.