Nobody is disputing your right to an opinion. You can have an opinion on anything; the crux of the matter is whether your opinion is persuasive at all.
It just so amusing that the authenticity of a Christian is determined by a non-Christian. It's like someone who himself does not believe in Christianity telling a Christian the correct way to practicing the Christian faith. It's not even theology; it's just common sense.
You appreciate that your freedom to have an opinion and whether you're qualified to give an opinion are two different species altogether.