It's hard to remove Smart Rule when there is no idea if it's used already in other Smart Rule in selection criteria.
The problem is:
we have filter for privileged accounts in smart rule called "A"
we use smart rule "A" in smart rule "B" to link privileged users to managed assets
by mistake we disable/remove smart rule "A" which leads to link managed assets from smart rule "B" to !ALL! managed accounts
From security point of view managed accounts still need to get rights to really login to assets, but at the end we need to unlink wrongly linked accounts which is not easy at all.... :)