This is clearly something that concerns you greatly.
Lots of alternatives to plastic are available - especially for something as common as a butter dish.
If you are unhappy with your purchase, as it was misshapen, you can open a return and send it back at the seller's expense.
If you bought a new item from a UK business seller, and you feel the item is unsafe, you should report it to trading standards.
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)