You're not defective. I also love the idea of horrible adorable Tiefling larvae.

Things that exist in my headcannon: The abilities of Thaumaturgy are instinctively available to Tieflings from birth [access to the Infernal language necessitates hearing it or seeing something written in it. It's like a key in a lock there] so when a baby Tiefling is upset, they can change the colour of nearby flames, amplify their voice, and/or twist the shadows into unnatural shapes.

I understand how this could disturb some folks.

Baby Elves, meanwhile, have instinctive access to the abilities of Prestidigitation. They get to sparkle when they're happy.

It's not fair.