How can one be critical of their religion islam properly, or is it a sin?

[sid]

how can one criticize islam, i mean not insult it ,but look at what one is following from a critical point of view, i mean how critical is one allowed to get, what things that you have had doubts about or are thinking of is ok to question or feel ,or is it a sin? how do you know, where do you draw the line?

[muslim720]

You are to have questions about the religion not question the religion.  You may ask why are women required to cover their heads; nothing wrong with that question and you will get a plethora of answers.  However, if you try to undo those answers then you've gone a bit too far; that is when you're questioning Islam.

In my younger years, I knew eating non-zabihah meat was a no-go but I would still eat it.  Instead of making excuses for myself and saying, "well the food of Ahlul Kitaab is halaal for us", I would admit that the shortcoming was in me for failing to follow that religious obligation.  Alhamdulilah, I've not had non-zabihah meat in almost 7 years now and this is coming from someone who loves burgers and steak.  At the time, there were not many halaal burger joints in Washington DC but it was not difficult for me to stay away; now there are so many halaal burger joints.  It is as though Allah (swt) was waiting for me to quit eating non-zabihah meat.  The day I stopped, within a couple of years, all these halaal burger joints started popping up, one after another...Alhamdulilah.