It is very rude to make fun of names in another language––are you German?––no matter how "infantile and ugly" they sound. I, for one, think it's very cute, such a nice alternative to "Friederike".
This is a gorgeous nickname, although for some reason it reminds me of those deep-fried potato cakes. I'd love to be called Fritzi, but it's a far cry from my real name, Bethanie.