[wmfights]

Thus He could never have been a mere man as He existed before mankind.

No argument from me. We exist at his pleasure.

I was unaware that Mormons believed God "evolved" from being a mere man.

[Bainbridge]

I believe it is stated as:
“God himself was once as we are now, and is an exalted man...and you have got to learn to be gods yourself.”
Journal of discourses 6:3-4 (Joseph Smith)

Now this doesn't sound too good. So the church is finessing it, and revising and developing and denying it and the verbal gymnastics required are absurd. But if you do some basic research you cannot avoid the fact that this is a foundational belief of the LDS church. And so no, they are not Christian.

[sevenbak]

I was unaware that Mormons believed God "evolved" from being a mere man.

That's because it's not true. It's one of many things the anti Mormons put out there to distort our faith.