I don't think its a question of the most tactful way to teach homophobia. You can tactfully teach your kids any kind of discrimination you yourself possess.
The tactless part is for an organization that benefits as a religion (tax exemption etc) to make a systematic cartoon aimed at children. Many groups are intolerant of people that are different from them, not everyone is making Pixar cartoons to demonstrate it! And this is a Jehovah's Witnesses discussion board is it not? Can we talk about why this is twisted they use members tax free dollars to produce this type of thing? To demand tolerance and freedom as a religion then turn around and so disgustingly (seemingly tactfully) make a children's instructional video?
They could have done' the same thing with something like shunning, polished it up into a nice little cartoon that would make the witnesses seem almost sweet about it, but we would all know exactly what the message is no matter how they deliver it.
Being a homophobic organization is low
Making a cartoon like this aimed at kids is lower...
FMF