With the exception of Alice in Chains (which was during the Hagar years and thus doesn't really count) they always took fairly shitty opening acts out with them, IIRC to avoid the risk of someone doing to them what they did to Black Sabbath every night on that first tour....
Speaking of the aforementioned "stupid and insecure" mindset, because back in the day, NO ONE was really capable of doing that to them anyway - but they took no chances.