Saudi's may very well go buy some Russian hardware, but at least it would be mildly more acceptable than being a western nation that shouts "democracy for all", then goes and sells a bunch of high-tech weapons that the Saudis can barely use so they can murder some Yemeni kid.
It's about proving to the world that there's a better way than arming everyone, Russia and the US realised this 40-50 years ago with Nuclear arms, why not conventional?
Perhaps Saudi Arabia will never revolt against it's stupid royalty, but we know for a fact that western weapons were used against (if not purely for intimidation certainly, unsure if anyone was killed with sold arms) Egyptian civilians and Ukrainians when they went against their incumbency... sure you can throw out the "responsibility is in the hands of the user" spiel, but i won't listen to it. (oh and add the now despotic Turkey to the list of wonderful allies with western equipment now also terrorizing it's people)