Because some people are too ignorant to listen to anything besides what they believe and refuse to listen to reason, some people just are very offended by the subject in general. People see differently from others, which will lead to arguments and other forms of conflict.
This site has a lot of athiests who sit around waiting for questions about religion, especially Christianity, so they can pounce and start attacking you and everyone who gives an answer that relates to the question.
They hate God, they hate the idea of God, and they can't wait to lambaste anyone who does believe in God.
I don't know, but every time I comment that I'm agnostic and an atheist, I get a ton of death threats and hate mail from religious people, even though I have no problems with what they believe in... I think it's just that so many people have had their own experiences with religion,and it can be hard to accept others' opinions.
Jesus himself went after the self proclaimed "religious" of the his day, the Pharisee's. One of the things he said to them in Luke 11:39 was this; And the Lord said to him, ?Now you Pharisees cleanse the outside of the cup and of the dish, but inside you are full of greed and wickedness. He also said told them to "love their neighbors as themselves" Mark 12:30-31. There are many that call themselves "Christian/Religious (usually by Christians)" bu they do not live "like Christ" and have tainted the label of "Christian" for those who try to live like Christ and glorify God by, loving their neighbor as they do themselves (work in progress). This doesnt mean protesting funerals with a hate agenda like that group from Westboro Baptist Church, they mar the name of Christian and Baptist in one fell swoop. There is forgiveness at the cross of Christ for them too. Sorry to ramble :-)
Because people like to be right, and like to push eachothers buttons when they feel the need to, or feel triggered to, it's all psychological kinda like boxing, I call it chatter boxing, but in this play only few can meet all rounds with the opponent, because many are too quick to anger and forfeit, others roll with the punches, then get tired out too soon, because of frustration, and others just roll with the punches and finish all rounds, it's just chatter boxing. oh and I'm an openminded, religious person, how does that happen, I'm not sure, but I'm here and I got no problem putting my perceptual views on the table neither will I exclude others to put theirs also and try to see it from their perspective, kinda funny but my religion won't let me condemn another's beliefs or views, judge not lest ye be judged, and whatsoever ever measure you judge so will it be to you also.