It's true! Look at all these facts:
*Impostoclaus has a rhyme just like the Grinch.
*Impostoclaus is taking his unlimited presents with him. Leaving town without giving us anything.
*Impostoclaus requires our "Winter Wishes" in order to get anything from him. We now no longer have any wishes left.
*Impostoclaus just steals random presents laying around in the middle of nowhere and takes them back to his batcave.
*He has a lackey that just happens to be dressed up like a Reindeer. A single Reindeer just like the Grinch.
*The Grinch was an "Impostor of Santa Claus." "Imposto Claus"
Don't deny it, it's all right there.
Because if he's the Grinch, what are the specialized gremlins he wants you to kill?