One thing that's sure to make me tune out a person in any discussion of race problems in the united states is the "my ancestors" statement. It's treated like it's supposed to be the ghetto pass of race talk, the thing that'll make me say "why yes you can understand all about my plight so your argument that racism doesn't exist must be valid oh color-blind messiah of kum-ba-ya".
I'm sorry, what?
How are "my ancestors" relevant? I'm not disputing the oppression of the Irish or how badly immigrants were treated upon coming here or any other group typically used with "my ancestors", not at all, but would you please explain to me how that effects YOU? Are you likely to run into an issue or be on the receiving end of prejudice, bigotry, and race-stupid today because of it? Probably not.
If I'm talking about the issues that I and other people in my similar "category" are working to dissipate currently, why do you think your argument about how several generations ago people you were related to experienced the same and oh! it's still happening in country X that isn't this one where you live is a needed insertion? Please, please explain how this is relevant and not your (maybe unintentional) attempt to divert by painting yourself as "just like you".
It's like the kid who wishes he had to wear glasses because all his friends have them; but just because you are not experiencing the problem on your head directly doesn't mean you'll be excluded from discussions on how to solve it, so why the attempted race pass? And if you're using it as a reason why you think you aren't part of this magic majority that often comes up, that's just as silly as "I have gay friends" or "black people can't be bigots".
When no one's pointing the finger at you personally and saying "shame on you White Man, shame" but you feel the need to somehow distance yourself from "white man"--that's telling; and when they are pointing the finger "my ancestors" only fans the flame. It doesn't "shut them up quick" like people who use it like to tout, rather it creates more tension and defensive attitudes when bridge-building ought to be the objective.
What happened to those ancestors is certainly to be included in broad discussion of the history of oppressed and/or ill-treated peoples in this country, and even in a global contemporary setting. However, when the topic is what's happens right here, today, charging in with "my ancestors!" when it's not directly relevant to the time-frame or country makes you look ignorant or at least (if well-intentioned) desperate for inclusion.