if statement executing if "value=" is found in file

I want to find every line in a text file that contains the word "foo". I set up my if statement like this...

for /f "delims=" %%i in ('type "%textfile%" ^| find /v /n "" ^& break ^> "%textfile%" ') do (
    set "line=%%i"
    setlocal enabledelayedexpansion


    set "wordtofind=foo"
    if not "!line!"=="!line:!wordtofind!!" (
        set "erase=!line:*=!"
        set "newCode=bar"
        >>"!textfile!" echo !newCode!

For some reason, the if statement executes when the string "value=" is found. Can someone please explain why that is?