I'm currently playing a bard and I picked up vicious mockery as one of my cantrips. My group and I had an encounter with some giant rats and I tried to use the spell on them, but the DM said they are not affected with this spell because they are not humanoids.
But reading the spell it says
You unleash a string of insults laced with subtle enchantments at a creature you can see within range. If the target can hear you (though it need not understand you), it must succeed on a wisdom saving throw or take 1d4 psychic damage and have disadvantage on the next attack roll it makes before the end of its next turn.
So I thought if the creature is capable of hearing me, it should be affected. Who is right?