Hoping this doesn't offend anyone

I've noticed a trend lately, among my African-American friends and colleagues.

Maybe it's a new trend, maybe I'm just now noticing it. Either way, it really bugs me.

This has occurred recently in conversations that I've been involved in, and in conversations that I've simply overheard.

When the conversation involves people of more than one race, and there happens to be a disagreement between people of different races (and the issue itself has nothing to do with race), the black person / people writes off the disagreement as being that the white person / people just can't and won't understand because they're white. Or because they're "not black".

Most recently this happened at work. *names changed to protect identity
Victor (white) and Todd (black) get into a discussion about politics, near my desk. The two best debaters in our group, I decided early on this was going to be interesting. A few minutes into the conversation, the topic narrowed to the health care reform issue. Victor was against it. Todd was for it. They go back and forth for a few minutes. Neither side is "winning". They both have valid points, strong arguments. Then Todd, seemingly out of nowhere (for me, anyway), declares that Victor is only against the health care reform because he's white, and doesn't understand what it's like to be black in America. No information to back this up. That is the end of the discussion. Period.
Despite the strong arguments, the very valid points presented by Victor, Todd dismissed them all in one statement. "... you're white..." It was as if because Victor was white, Todd didn't have to... nay, shouldn't.... even consider the possibility that there was any legitimacy at all in Victor's argument.

When I see or hear this happening, it's as if the two can't possibly be disagreeing just because they disagree, but that the entire reason that the white person doesn't agree with the black person is because they are white. Again, even if the issue itself has nothing to do with race. As if there can be no other reason.
Any intelligent conversation stops, and everything is paused, held there in unresolved limbo, when the race card is played.
As a white person, there's nothing more you can say. Your opinion has been written off because of the color of your skin. As having no legitimate merit at all, because you're white.

Why this bothers me:
While I acknowledge that I, as a white person, don't know and will never know what it's like to be black, I also acknowledge that we all, as individuals, don't know and will never really know what it's like to be anyone other than ourselves.
That the idea of not knowing what it's like to be someone else isn't relegated to race, gender, religion, sexual orientation, marital status, etc. but is simply because we are all different. Period.
So, to write off someone's point of view as being not relevant, as not having merit, as not being worthy of serious consideration simply because they are white, because of the color of their skin, is by definition, a prejudiced way of thinking.
Because the more I see and hear this, it seems to be an excuse. A made up reason to not have to consider a differing viewpoint. A way of taking the easy way out. Not just with others, but within themselves.

That is why this bothers me.