That's right; they can't just say, "Oh, I'm guilty of random sinning & so Jeebuss paid for all that
" but they have to admit one specific sin: the sin of 'just going along with their leaders' destructive decisions' like the people of His day.'
Here,
Jesus points out to the Pharisees how the very prophets who wrote their laws were the ones who were turned-against back in
their day ... just like Jesus, the prophets disagreed with the
status quo, and died for so-standing. And 'the will of the people' (OUR will, while we're sitting at home hearing about it in the news) was firmly on the side of the
status quo, NOT Jesus-&-the-prophets' side.
And--even though He was innocent of any death-worthy crime--He submitted to die! And as He died, He
didn't say 'Father, forgive them for they
follow you in My name," or 'for they
believe I was born of the Virgin & was anointed by the angels & did miracles etc.'; He said "Father, forgive them for
they know not what they are doing."
So the sin we must plead guilty to is 'making decisions (as we sometimes must) without knowing what we are doing.' Just like Joseph's brothers were forgiven for selling him into captivity (not knowing that they were saving the world from death-by-starvation), WE are forgiven for 'going along.'
That's something I notice happening more-&-more today: people aren't as concerned about who's "right" as they are about who's (as the witch said to Jack & Rapunzel's parents in the Musical
Into the Woods) "nice"---no one seeks vengeance for "tax-evasion" like they would for "murder."
Back to the Topic: We must plead guilty of holding 'the way things are' to rule over 'the way things ought to be.' Jesus was against the people's "way things are" and so had to be eliminated; the people didn't care that His was "The Way things ought to be," just that He was messin` with "the way they had it figured-out."
Maybe
that's the specific sin we're guilty-of: thinking we have the right way figured-out (a more-specific description of "Pride"), especially if we just 'go with the flow.'