# O, 8 bytes

    {_.@_-=}

An anonymous function that takes a character and a string.

[Try it online.](http://o-lang.herokuapp.com/link/J1QidGVzdCJ7Xy5AXy09fX4=/)

## Explanation

    {_.@_-=}
    
    {      }
     _        Lowercase string
      .       Duplicate
       @      Rotate stack
        _     Lowercase character
         -    Remove all instances of the character
          =   Compare to original