Why are Athiest's and other's afraid to Defend thier stance on Religion?

I recently joined another Social Network of which I will not mention. Thinking this was just another Christian Website I posted my comments on a subject called "how can we be 100% sure God is real". Being a Theology student as well as a Pastor I went to work and did what any God fearing Christian would do and defended my Father and his Word. I do admit I can get long winded at times and this time I may have done that but all my intention was, was to give evidence that the Scriptures were written by divine inspiration. Upon finishing I left the site and received an email stating I am being accused of Drive-by Preaching, in other words you can defend your Faith just don't bring God or the Bible into it. Why are they so afraid of the Scriptures? Is it because deep inside they know there wrong but are so wrapped up in todays society they are afraid to admit it? I really hope someone can give me some insight on this, why deny something if you have no proof to prove its fake but on the contrary have hard evidence it is real, it is divine it is from God?