While I enjoyed those older cartoons as a child, now, as an adult I can totally see why they are no longer screening. They were rife with racism, violence, sexism and other crap that I wouldn't wan pumped directly into my child's brain. Children don't have filters, they ape what they see, and you don't really want your children walking around saying things like "Boy, I say boy...".
Even shows like The Flintstones are rife with undertones of wife abuse and domestic violence. I don't recall any specific racism in them, but that might be because every single character was suburban and white.
Road runner was entertaining, and I don't recall any overt racism or sexism, but it is just silly violence for the sake of violence and I think we can do better for our children. I don't oppose the use of violence in cartoons, but there should be more there for them to chew on.
Elmer Fudd is currently on TV playing the character of Kripke in The Big Bang Theory. It's cheap laughs at what is for a very few people is real problem. I prefer to avoid bullying humour or humour that works by undermining another person. It's weak and it hurts people's feelings. You may not know anyone with that speech impediment, but I can assure you there are people out there with it and while some might laugh, others might feel it's personally hurtful.
I'd rather my kids watched something funny, cool and nourishing - like My Little Pony or some of the anime out there. Something that shows choices have consequences and teaches them morals lessons (without being heavy handed). I won't mourn the passing of Saturday morning TV.