f a situation arises where if you were to pull hate you or your alli would be in trouble, -5 enm won't save you.
This is just the "if I can't get them 100% clean, why even bother washing my hands??" argument, and it fails. Balanced measures for hate control work fine, and in fact are how hate control in general functions at the alliance level. Would you tell your tank not to equip +5 enmity because, hell, you're just gonna pull hate anyway? Hate control is not an absolute -- it is a balance between players, and reducing your own enmity is the same as increasing your tank's when it comes to whether you will pull hate or not.
-5 enmity might not be a good trade for a SAM that has something amazing in the ammo slot, but compared to a puny Tiphia Sting it's a solid option, especially in cases where you're holding back enough that the Tiphia Sting might literally be providing zero benefit.