Depends on the cartoons I guess.
Sponge Bob has a pretty widespread appeal, even with some adults. Sponge Bob uses NFL Films music (the old stuff written by Sam Spence) in some of the scenes and often makes direct and indirect references to vintage TV, film and pop culture subjects.
I will ocasionally watch older cartoons that I liked as a child (Scooby Doo, the Superfriends, the Flintstones, the Jetsons, Johnny Quest and etc.)
Does he have children? I have four kids, so obviously Cartoon Network, Noogin and Nick are channels that appear on one of our TVs quite often.
But if this dude is watching shit like Pokemon, Dora and the Power Puff Girls....then yeah, maybe there's a slight cause for some concern.