Method to filter out objective statements (or say facts)
There isn't really an "objective" statement.

In your example: what if he wasn't born that day? Same statement, but is it still objective?

You may assume that "1 + 1 = 2" is an objective statement. But what if I'm doing binary math, and 1+1=0 then? So even that is subjective.

How would a machine tell apart these things, where philosophers will disagree with each other?

All you can do is provide training data examples of "your" (subjective) idea of objectiveness.