Should parents let them know?

So I saw this on Facebook right now, and it made me wonder... if the father and mother “knew” their child was gay at 6, why didn’t they tell him that they knew when he hit high school or a certain age?

To me, I see a lot of teens terrified to tell their parents, or coming out.

So basically my question is, if the parents have had a feeling for a long time that their child is gay, etc, should they mention it to the child and save the child from being scared to tell the parents?