So basically then, you just dismiss the evidence, the arguments behind the evidence, and everything else that supports the evidence,
What about Josephus? Josephus mentions Jesus twice. Josephus places Jesus in the very recent past, names James (a contemporary of Josephus), as the brother of Jesus, and gives us a basic outline.
Josephus has nothing to do with the dating the early Gospels, which was what Egyptian Phoenix was doubting. We already know that Josephus was tainted by some interpolation, but many scholars feel strongly that it isn't all interpolation. Since what he wrote was based on unsourced information that he got from other people, it is hard to use Josephus as clear evidence for historicity, even if it were completely unaltered from the original. All it would mean was that Josephus, writing decades after the facts, had concluded that Jesus was a real person.
The evidence from Paul that he had visited James, "brother of Jesus", seems to be the strongest evidence we have for the historicity of Jesus. There are other arguments, but this one appears prominently in defense of historicism. It is still a very weak reed to hang an argument on, because Paul says nothing else at all about the relationship. Carrier and other mythicists have taken the position that there are a number of ways to interpret that statement that do not support historicity. He seems to favor the claim that Christians routinely called each other "brother", that this practice is well-documented, and that he may have used that rubric because he considered James not to be an Apostle, unlike Peter. Carrier claims that the Greek could be translated to mean that he had not met another Apostle except Peter and Brother James, the implication being that James was a Christian, but not an Apostle. Not being able to read the original Greek, I can't judge Carrier's argument, but it strikes me as a bit of a stretch to claim that James was not an Apostle. Peter, James, and John were names of the three "pillars" of the movement, although a lot of people were named "James".
Ehrman asks why Paul did not also refer to "Brother Peter", as it were. He thinks that the correct expression would have been "brother
in Christ", not "brother
of Christ", if Carrier's meaning were correct. Carrier has argued that
brother of in Greek is actually ambiguous between biological and adoptive interpretations, and that all Christians were regarded as having been adopted by God. They called each other "brother" all the time. So I don't see that quote as having quite the significance that historicists think it does, but it still has significance as evidence.
Having read different English versions of Galatians a few times now, I am struck by the extent to which Paul considered Peter a rival and, quite possibly, hated him. Paul saw himself as in charge of bringing the Gospel to Gentiles, and Peter to Jews. So he seemed insulted that Peter deigned to eat with Gentiles, but changed his friendly tune when other Jews showed up. Peter seemed to want to convert Gentiles to Judaism, whereas Paul felt they were free to violate Jewish laws and still remain Christians. Hence, another interpretation of the passage could be that Paul pointedly would not call Peter a "brother of Jesus", because he did not respect Peter's attempt to preach a false Gospel to Gentiles, who were, after all, supposed to accept Paul's teachings on such matters.