Was Christianity invented by Constantine?

Yesterday I explored how the science of memory could have affected the origins of Christianity, because the bible was not committed to writing for decades after the alleged events occurred.

I also mentioned that I consider that sort of distortion of the truth to be accidental and not meant to mislead people deliberately.

However . . .

Some people do think that Christianity had a more sinister origin, as is described in this article from the Beyond ALL Religion blog, in a post called How Christianity was invented. which begins:

Christianity is a copycat religion created by Emperor Constantine (for political purposes) based upon a myth (The Persian savior god Mithra, crucified 600 B.C. ?  400 B.C.?), which was based on other similar myths, all the way back to Chrishna of India (a mythical god that some claim was “crucified” around 1200 B.C.). There were 16 mythical crucifixions before Christ. The belief in the crucifixion of Gods was prevalent in various oriental or heathen countries long prior to the reported crucifixion of Christ.  Of the 16 crucifixions, most were born of a virgin and about half of them on December 25th.     Read on.

I'm interested to hear convincing arguments against the facts that have been presented there, as they appear to be quite compelling to me.  Just seeing Chrishna spelt that way seemed to add to the story - although I am sure that is not convincing and rational evidence.

See some related posts from Something Surprising:

• Horus and Jesus 
• Mithra and Jesus  
• Krishna and Jesus
• Not even a new myth!