I don't like Undertale, but it is not appropriate to ban someone when they joined because of the server name.
What I hate even more is people change the server mid-session with a "should i chang the serv 2 fnaf famili rp OGM!?!?!?" voting poll. After everything gets deleted, I never get to use the fortress that I was building for over an hour, let alone see the light of day touch it ever again. That happened to me two years ago.
Even though someone has the right as the owner to change the server to what they want, it doesn't mean that they can disregard your time and effort in the blink of an eye. They should at least consider that before starting a server. I've gone on a tangent, but the principle is the same.
/maximum support.