I think there is a more developed back story to Jock. We don't know about Clayton's rise to power, but in the Dallas universe, it is
entirely possible, maybe even likely, that he used the same tactics as Jock. Therefore it can't be assumed that the Clayton of post-Jock Dallas was a paragon of ethics.
I've often wondered why Jock was put on a pedestal by The Ewings as well as the viewers. I think many of us were so touched when Jim died so early into Dallas and we respected him as head of the family and part of the ensemble cast even though we knew he was no angel.
Maybe we need to be more forgiving of Clayton (agreed that punch was a cheap shot)
We knew most of Jock's background, but I always felt there was more that was only referred to as regards to his "bad" behaviour in his younger years.
In the episode John Ross Ewing III (part 2) Miss Ellie and Jock discuss marrying into the family and having the Ewing name and money. Miss Ellie says to Jock he was born a Ewing and didn’t have to marry to get the Ewing name. Jock says to her "you did",
Miss Ellie replies, "but I never needed the Ewing name, I was a Southworth and always felt secure in your love, except maybe once or twice". This is before we learnt Ray was his son.
He also said to JR that he never begrudged his boys having a good time
"Hell I did" he told his son.
We knew he could be ruthless in business and went along with JR about finding skeletons in Cliff Barnes' past and to do "Whatever" when JR said if they're weren't any, he would put them there.