Did Jesus Christ exist as a historical human or was he a theological construct?

[Minimalist]

Have you ever compared the lore associated with Jesus to the mythology of the Persian god Mithra?

Check it out: http://www.near-death.com/experiences/origen048.html

Some of this needs to be taken with a grain of salt.

Chambers Encyclopedia says: "The most important of his many festivals was his birthday, celebrated on the 25th of December, the day subsequently fixed -- against all evidence -- as the birthday of Christ.

While true it ignores the fact that the Romans had a traditional start of winter festival, the Saturnalia, which went back to the 3d century BC. When the cult of Sol Invictus (as the Mithras cult was known) was imported into Rome it too either was fitted into existing traditions or fortuitously did fit into those traditions. It is not so odd. Many cultures had a winter celebration.

Some of these 'similarities' between Mithraism and xtianity are a stretch but some seem quite real.

While it is true that the Vatican Hill was seized by xtians in a land grab this was far from uncommon. Excavations on Vatican Hill have dug up shrines to many earlier gods, including the Cybele and the site was a cemetery for a long time. Building or usurping the religious sites of older gods is a common theme in many places. NO reason why Rome would be any different.