I really have no problem saying I like Spongebob tbh, I mainly watch Spongebob because of how fluid the animation is, I also like the comedy in the first 9 seasons, not to mention it's one of the few nowaday kids shows starring adults, Spongebob is a good show and you should have no problem liking it. If people make fun of you for liking Spongebob they are just pushing buttons, or they could just be joking, but all in all, if bullies do actually make fun of you for liking Spongebob then they are just looking for material to work with, you don't have to be afraid to admit it.
I am one of the biggest spongebob fans at my school, and I have been made fun of for liking the show. It's kinda stupid to me because much of the internet culture between teenagers is surrounded by spongebob memes, but it's whatever. Life is too short to care about what people think of you, just watch what you wanna watch and that's my advice.