We can add points to regression line but we can't remove points from regression line.
We can ignore but it is not good management especially if you added a wrong point to the regression line that must be added to another regression line. Because the point, even ignored, belongs to a regression line, you can't add it to another. It means you must delete the regression line and do it again.

So we really need a command to remove point, or selection set of points, from regression line.

We don't want to delete the points. Just remove them from regression line.