As with "Tinky Winky", the "is Spongebob gay" rumors started among the secular crowd before being picked up by religious "leaders" (and they are about as representative as Jesse Jackson...).
That's free speech, can't stop someone from talking.
The NEXT video in classrooms, Contraceptive Spongebob, will make it abundantly clear to children that Ol' Squarepants has been intimate with womens' most private parts.