Most of the characters who use violence regularly are the "bad guys," so to speak. Effective parenting would also involve teaching children that using violence without reason is bad, and makes you a "bad guy like those rascals on TV." Just be sure you're instilling the right values in your children, and that is sufficient to combat any "themes of violence" in these shows.
Looney toons are not that violent at all. During the show,they do a lot of crazy things towards eachother,but I wouldnt consider that violence at all. It is just a ton of nonsense for the purpose of making people laugh. So Loony Toons are not violent one little bit. P.S I spelt looney tunes wrong as a gimmick.