Sure. Sometimes, when a character says something on the show it's signposted as being self-interested, or All About Them. BtVS does that often enough to be a trademark, in fact. I don't think Xander's was that sort of speech. I think it was the writers saying to us "Here's one interpretation of the Buffy/Riley situation which we think is a valid approach to take; please consider it." The're not saying it's the final and ultimate truth, but it wasn't presented as being wrong either.

Which is where I think that polarisation we were talking about before comes in. Far too many people seem to assume that if you say the blame isn't entirely 100% on one person, you must be saying that it's 100% on the other. (Personally, I tend to think that Riley had a valid point about Buffy's inability to open up and share with him, but the way he went about trying to express himself was wrong, and she had a damn good excuse for behaving that way at that particular time in her life. But nuances like that seem to get lost too easily.)