marmaidophobic
Do you mean being anti-mermaids? I found the term:
Mermaids were propagating rapidly and it became a real problem for the local fishermen.
There were some hurtful stereotypes regarding mermaids and they would really like you to come to them, so they can tell you more about it.
Media was really lying to you, when they sold you stories about beautiful humanoid creatures with amazing hair.
Their impossibly sharp teeth weren't even the most horrifying thing about them.
Catching a mermaid in a net was a really bad omen.
There was nothing scarier than being trapped on a boat surrounded by hungry sirens.