The implication is that this is an act of childish behavior, like burning a flag, except, well, less dramatic and with less hygiene involved.
"If I disagree with you, I will have special toilet paper made with your picture/symbols on it and wipe my ass with it." How is this any sort of logical adult reaction?
It is up there with "Nanny nanny boo boo", and "up yo' giggie with a wah wah brush!".