Jassy,
"but this country was built on Christian values of kindness, tolerance, etc' as I've seen many times on MN."
In a Venn diagram, personally, I view values perceived as Christian ones, overlap with many values non religious people hold. The history of this country is largely Christian, this cannot be denied - thus the values of Christian people are implicit within many of this country's laws. This does not mean other non Christian people do not hold the same values, or that these values are exclusively Christian. Rather it is a reference to this country's heritage. As I see it, anyway. This should not be used to 'alienate' in anyway though.
"I'm a little confused by what this paragraph is addressing. Is it challenging the idea of uniquely Christian values? I don't think this falls into the same category as belief in the Christian god, where I wouldn't challenge someone's belief unless they were trying to impose their belief on me, either directly or via policy, or if they were trying to claim factual/historical evidence for the existence of God."
I made the statement in reference to where you said this,
"I think we'll have to agree to disagree that those values were unique to or somehow derived from Christ and Christianity; I think the evidence is pretty strong that they aren't and didn't (and there is also, as Bertrand says, the fact that the values embraced as 'Christian' change greatly over time, and Christianity trails behind the prevailing cultural idea of morality at least as often in history as it has been seen to lead)."
It was not intended to challenge what you say re. 'Agreeing to disagree' but rather the way you portray an argument concerning the source of goodness/morality. You refer to 'evidence' regarding development of these values, suggesting you are right according to the available facts. It is not something that, I believe, can be proved. The evidence is too scant, with too many variables, to be presented in anyway that 'trumps' religious belief, IMO. But since that puts this (your argument) in the realms of belief there is nothing to really comment on unless you are portraying this as an established fact.