Depends on your individual LO - I let my nearly 4yo dd watch it but mainly because she very very rarely repeats things she hears on the tv so the language doesn't matter so much, and cartoon violence doesn't seem to phase her at all, she doesn't really get it, she thinks it's funny in the same way as Tom & Jerry.
May stop her watching it when she's a tiny bit older and a bit more impressionable tho. She only likes it for "the spiky baby" TBH!!!