In 2008, there was scrutiny re candidate Barack Obama's affiliations re his church/Pastor Wright, along with Bill Ayers.
Nominees for the federal bench undergo great scrutiny. Because our country believes in separation of church and state, it is fair game to vet judicial nominees who may or may not have overzealous religious beliefs that may taint their ability to be fair and impartial jurists.
Certainly, using partisanship to attack one's religious beliefs is inappropriate. But, if there are genuine concerns re whether a nominee has an over-the-top religious or anti-religious agenda, I expect Senators to scrutinize the information in good faith, but respectfully.
You assume everyone views the Knights of Columbus as you do. Some view KOC as too political -- the Catholic Taliban types. [I have no opinion. Have always declined when asked to join]
Affiliation with any religious or secular group should be viewed in proper context. The starting point should be deferential to the nominee.