Xenophobia is one thing, but what he was trying to do is way beyond that, and considering the odds he placed himself against, he would have to be mad to think he could win. Though, speaking of methods, I wonder what his previous "brilliant plans" were?
It also seems that he took to being a "Lord's Son" far more enthusiastically than Lucian did, Julian must have wanted his son to be just as he was at his age, in the very same way that his own father wanted Julian to be like him before he was assassinated. Of course, this is merely speculation.