In the following verse of Holy Quran you will read that the humans will never end their question. The curiosity of the humans never ends. We always try to ask the question about every thing. We always want that we know more and more and even in the thrust of knowing we ask the stupid question. Same situation occurs when Allah commanded the Israel's to sacrifice a cow. If they will not have disease in their heart they will just sacrifice any cow and Allah will accept the sacrifice. But besides to obey the command of Allah they start questioning of different things as mentioned in the verse mentioned below:
"The said: Call on your Lord for our sake to make it plain to us what her color is. Musa said: He says, Surely she is a yellow cow; her color is intensely yellow giving delight to the beholders."
(Para No: 1 & Verse No: 69)
They are asking such question because we did not want to obey the commands of Allah. This is the main problem we said that we believe but we will not follow it. We said that we like the things but we never try to implement one thing in our life. This is the problem we just read and ignore never try to implement in our own life. It is very difficult for us so we will start questioning and if some logic and thoughts are according to our mind then we just follow it. This is the main problem of sectarianism.