I'm not a scientist too, just a lousy lawyer.
But continuing:
So, how does coldness hurt an adamantium golem?
How does coldness hurt a skeleton?
How does coldness hurt a shadow?
How does coldness hurt an earth elemental?
If you have enough knowledge or enough imagination to come up with a fantastic explanation for all that, or just accept those as possible and believable, it shouldn't be so hard to accept that "a creature made of cold energy can be hurt by a magical attack that inflicts an even more harmful cold energy, or just more cold energy that the cold creature could resist", or any other exaplanation one can make up.