Do Non-Christians Need To Cite Christians Who Agree With Them?

I was recently involved in a discussion with a non-Christian at another web site. He told me that I can't cite Biblical sources in support of my view of Christianity, apparently because of the bias of those sources. They're believers. I was told that I can't cite Christian scholars either. Even if a Christian scholar argues for his position and cites supporting evidence, the arguments and evidence don't matter. He's a Christian scholar, so he can't be cited. He's biased.

Does that sort of reasoning work in reverse? Critics can't cite somebody like Josephus against Christianity unless they can document ancient Christian sources agreeing with Josephus on the point in question? We can't accept, say, an objection based on the problem of evil unless a Christian can be cited agreeing with the objection? You can't quote somebody like Bart Ehrman or Richard Carrier unless the quotation is accompanied by the citation of a Christian source who agrees? And since I'm a conservative Evangelical, do the corroborating Christian sources need to be conservative Evangelicals, not just professing Christians of any sort? How does that type of thing work?

If the reasoning does work in reverse, it's odd that I don't recall ever seeing a single critic who uses this sort of objection against Christianity applying it consistently. They never seem to think they need to cite Christian sources in support of their objections to Christianity. Even if they do occasionally cite Christian corroboration of a position they take, that citation seems to be something they view as optional, not something they're doing because they think they need to. They raise a lot of other objections to Christianity without citing such corroboration at all.

Seems like a double standard.