I'm astonished and disappointed at the level of vitriol and intolerance shown in this thread.
Heisig used allegory from Christianity, Buddhism, myth and fable. His writings are typical of someone with a strong classical education. Most here have not had such an education. A small number of posters here appear to have hardly had an education at all.
At no stage in his books does he attempt to proselytize.
Rather than take umbrage at non-existent and imagined sleights, why not take the opportunity to gain some incidental and fascinating snippets of knowledge. Reading Heisig can introduce one to the Golden Bough, the tale of 桃太郎, and more.
If individuals then wish to re-craft their stories in the context of Mickey Mouse, Robin Hood, or Maggie Thatcher, then they should do so. That's what this method is all about, and Heisig simply gives a good leg up along the way.