They put it up on Murray Hill's busiest street. How could it not reflect their opinion of how Murray Hill would receive a big FU posted so prominently?
The logo is in the color Orange, which is close to Red, a color of aggression. The logo is also in a sort of gothic font, reminescent of Lovecraftian themes, which evokes feelings of dread in all residents. Some may say that the "FU" actually stands for "Fully Undressed" which is a dogwhistle for satanism, in that Satan will come to the earth and wreak havoc upon the residents (in this case, residents of Murray Hill) in a FULLY UNDRESSED state, which is clearly the intention of their sign, to warn the residents of Murray Hill of their sinister pizza-satan operation (Pizzagate, anyone?)
WAKE UP SHEEPLE! You're being indoctrinated into satanism by the insidious pizza place storefront sign! The message to the residents of Murray Hill could not be clearer. "Eff You, you will succumb to the influence of Satan, feeble Murray Hillians"