I feel like if the spray is going to drive people away, even if it is PG-13, it shouldnt be allowed(Maybe talk to the person who sprayed it if enough people complain about it). Granted, alot of someone not liking a spray is based on personal opinion, but as anyone on the internet knows, MLP is heavily criticized by most people online(so spraying something of the sort is basically baiting a reaction. Doesnt mean they cant spray it, but they should expect these reactions). If i joined a server and saw two ponies wearing panties and spreading there legs, i wouldnt wanna see that shi.t. Granted csgo doesnt have sprays(soon^tm), in css id have to deal with tons of inappropriate or offensive sprays, swastikas, spinning d.icks, you name it. im sure the tf2 staff is dealing with the same.
I might be from cs but since this is more of a relatable rule that ive had experience with, i feel it was handled properly, minus the slight bias that was owned up to. The spray is borderline inappropriate, leaving it up to the individual to decide if its inappropriate or not -1 for any punishment.