Some years ago I heard a joke that went like this: "Why don't blacks intermarry with Puerto Ricans?" "They're afraid their kids will be too lazy to steal".
Yes, that's racist, because both groups are being hung with negative stereotypes.
Contrast that to this: "if a married couple in Arkansas gets divorced, are they still brother and sister?" That's not racist, because you can say anything you want about poor rural whites. Liberals, the self-appointed arbiters of all things racist, think this is ok.
Now contrast it with this: in Crystal City, MO, a teacher was asked what she thought of intermarriage between races. She said she was against it, because it produced children who might be persecuted.
Although that might be a lousy reason, that is not racist on its face. IMO she's simply acknowledging that racism exists, and that interracial kids aren't always accepted for that reason. Whether they should be is beside the point - we have to deal with the world as it is.
Interracial kids do sometimes have trouble being accepted - they're not all like Halle Berry or Mariah Carey. Whether that's reason enough not to have them is up to individual parents.
I don't know what else the dismissed teacher might have done to warrant such a charge. The point is that the article Erin O'Connor identified doesn't give enough information to reach such a hostile conclusion. Nor was Erin O'Connor racist in taking the teacher's side. O'Connor writes more here
If charges of racism ever lose all meaning and impact, it will be because of manufactured grievances like this. Brandishing it this way is simply dirty politics.