Is it grammatically correct and natural enough?
✅It is sad to watch people being blind,even though the truth is poking them in the eyes actually.
Your use of "being blind" feels too close to a handicap, and thereby comes across as insensitive. The image of "poking in the eyes" is also repulsive. It is too ugly to be used in such a metaphor. Instead, I suggest that you specify what it is that they are unmindful of. As an example, I'll use "blind to the facts":
"It is sad to observe people being blind to the facts, even as the truth literally stares them in the face."
Note also that I used an active verb, "stares", rather than "staring". Your original sentence contains no active verb except for "is". (An active verb has a subject. "Staring" would act as an adjective, not a verb.) Active verbs will improve your writing. Try to give every sentence a subject and an active verb. It is not necessary that every single sentence have one, but try.