Luke 23: 34, "Father, forgive them, they know not what they do"

Luke 23: 34 in the New American Bible, Revised Edition (NABRE), reads: 
"34 [Then Jesus said, “Father, forgive them, they know not what they do.”]*"

the footnote (*) reads:

"* [23:34] [Then Jesus said, “Father, forgive them, they know not what they do.”]: this portion of Lk 23:34 does not occur in the oldest papyrus manuscript of Luke and in other early Greek manuscripts and ancient versions of wide geographical distribution."

I find this troubling.  the footnote tells me that Jesus didn't say "Father, forgive them, they know not what they do"--somebody(ies) added it to Luke's gospel later.

here's what some biblical scholars (author and commenters) say: Evangelical Textual Criticism: ‘Father Forgive Them’ – The Variant in Luke 23:34a 

did Jesus say "Father, forgive them, they know not what they do"? or didn't He? 

if Jesus didn't say "Father, forgive them, they know not what they do", then what does that say about the rest of the bible?

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Jean Le Tavernier [Public domain]