They also have a common custom — taqqiya.
The only time there is trouble is during the Shi'ite times when the YOUNG Shi'ite man beat up on themselves in penitential fervor. It is FROWNED on and FORBIDDEN by the Saudis so...the soldiers come in and beat the living tar outta the Shi'ites in Saudi Arabia.
Then, it's over and done with.
My boss was a Shi'ite.
There are TONS of holy sites for BOTH Shi'ites and Sunnis in and around that area.