way of accomplishing that goal is to choke off his oil revenues from Europe, and in order to pull that off, we need the assistance of those with sufficient reserves to increase production and sell it to the Europeans...Saudi Arabia fits that bill...however, the heir to the Saudi throne is an enigma (see link)...while his murder of Khashoggi was heinous, he has some redeeming qualities...and...since we already partner with SA in several areas, it's not irrational for us to continue to "do business" with them.
It would be nice if we could reduce all the complexities of world politics and economics to simple yes/no decisions, but that almost never happens...e.g. we abhor authoritarian communism, but we still have our computers and many, many other items made in China...and we used to buy Russian oil...in short, you have to prioritize what's most important to our national and the world's best interest...if that involves making a deal with Saudi Arabia...we do it...it's sometimes called "Prudential Judgement".
Link: https://www.vox.com/policy-and-politics/23141651/gun-control-american-approval-polling