Another mod that turns mobs passive, but not towards everyone, everything, or all the time.
The effect of Peaceful Aura can be applied to you (the player) and any mob (including the wither and ender dragon).
The effect is two-fold; It will, for as long as it's active, stop other mobs from targeting and attacking whoever has the effect (but as usual towards everyone else). Any non-passive mob with the effect will also be passive until the effect wears off.
Get the effect by eating a baked poisonous potato (1 min effect duration), or by a potion of Peaceful Aura (3 or 8 min duration). Other mobs get it by the splash or lingering potion variant of it.
To make a baked poisonous potato, place a poisonous potato over a campfire, in a furnace, or in a smoker.
Make it a potion by throwing the baked poisonous potato into a brewing stand. (The rest follows the same vanilla Minecraft brewing procedures.)

Regardless of having the effect: