Tools like this will always do more harm than good. False positives will always be sky high. On one hand it will obstruct the legitimate discussions and on the other hand it's trivial to game such systems. Toxicity won't be stopped but magnified by stimulating offenders to embed it in benign words and sentences. Quick examples:

  10% Holocaust was amazing. We should do it again sometimes.
  12% Would you like to buy some knee grows?