Probably not, because $read(blacklist.txt) reads a random line, you probably want to test if ANY line == the $nick.
Code:
on @1:op:#: {  
   if $read(blacklist.txt,s,$opnick) {    
      mode $chan -o $ifmatch 
   }
}

That tests if there is a line in the file that starts with the value of $opnick. I also added the @ to make it so it doesn't trigger if you are not an op.