One thing ive noticed with films of the 1970s is they were big on blasphemy.

1970s was more overtly blasphemous in movies than even today in many cases. Take a simple adventure movie like Poseiden Adventure and the anti-God theme is a heavy element weaved throughout the picture.

Clockwork Orange has some of the most blasphemous stuff Ive ever seen.

It seems because the 70s had some of the least studio interference, the artists tended towards that a lot when given free reign. The 80s and onward after Star Wars got more profit focused and a lot of that overt blasphemy in movies went away.

One other interesting example in the 60s is Planet of the Apes. The average person will tell you that its a racial allegory.

Surprisingly when I watched it, thats not even really a theme. The actual plot and theme is a pro evolution, anti-Christian plot.

The theme all throughout the first planet of the apes is that Charleton Heston saying what humans are challenges the apes religion and supports the few "brave ape scientists" who have been doubting the ape religion and pushing for the theory of evolution. Towards the end of the movie the religious apes even admit they knew that humans evolved from apes but wouldnt let that knowledge be known or else it would have destroyed their position of power.

Bizarrely the Planet of the Apes has little to do with slavery and racial allegories as it's made out, and far more to do with pushing a "Christians are suppressing science and denying evolution" message.