Yes, skeptics demand extraordinary evidence for Christ but don't demand extraordinary evidence for Alexander the Great who did the extraordinary thing of conquering much of the known world.
Callisthenes -- his works have perished
General Ptolemy -- his works have perished
Onesiscritus -- why do use someone you call "the liar" a source?? But I can understand why you called him the liar. Here is a passage from your source:
"Though an eye-witness of much that he described, it appears that he intermixed many fables and falsehoods with his narrative, so that he early fell into discredit as an authority. Strabo is especially severe upon him.[12] Plutarch cites him as one of those who related the fable of the visit of the Amazons to Alexander, for which he was justly ridiculed by Lysimachus,[8] and Arrian accuses him of falsely representing himself as the commander of the fleet, when he was in truth only the pilot.[13"
And here are passages from your last source:
There are numerous surviving ancient Greek and Latin sources on Alexander, as well as some oriental texts. None are contemporary.
The primary sources written by people who actually knew Alexander or who gathered information from men who served with Alexander, are all lost, apart from a few inscriptions and fragments.[1]
Here is what the book cited in post #1 says:
"The truth is, we base virtually everything we know about the "extraordinary" life of Alexander the Great from historians who wrote 300 to 500 years after his death! In light of the robust evidence for the life of Christ, anyone who doubts Christ's historicity should also doubt the historicity of Alexander the Great. In fact, to be consistent, such a skeptic would have to doubt all ancient history."