Is it reasonable to condemn something that one does not know?

No.

It is NOT reasonable to condemn something that one does not know about.

It is reasonable to question, listen to answers and have debates, do your research, form your own opinion and politely disagree. There is much merit in all religions, but there are many false prophets in all religions also, who lead their flocks astray.

At some point in our lives, we Christians were not Christians. We were unbelievers just like everyone else.

- You were born that way, but you had yet to be indoctrinated into what needs to be "un-believed".

I know what it means to be an unbeliever today because I was once part of their number and can see the difference that God has made in my life.

- Followers and "believers" said the same thing about Hitler, Stalin, Mao and even Idi Amin.

How then can a person who has never had the personal relationship with God possibly condemn those of us who do?

- We understand being suckered, just like I said above.

Isn't that like saying....Chocolate ice cream is not real when you have never had chocolate ice cream?

- Nope.

In all the years I was a Christian, I was never able to get anyone to describe what "having a personal relationship with God" meant in terms that meant anything to me.

There is a principle

which is a bar against all information,

which is proof against all argument,

and which cannot fail to keep man

in everlasting ignorance.

That principle is condemnation before investigation.

- Edmund Spencer

You don't have a personal relationship with god, you have a stirring of emotions at church that you LABEL a personal relationship with god.

"We were unbelievers" - yes, you mean when you were born, before your parents introduced you to the myths at a young age, too young to question it.

By that rationale, how can someone who has never killed condemn murder?

No.

Christians are the only people who have been on both sides of the fence and know enough to evaluate both atheism and Christianity.