Nor should you. Even I agree Poltergeist having a PG certificate is insane. Fun fact: Both Poltergeist and E.T. The Extra-Terrestrial, released around the same time, had PG ratings in America. In the UK, E.T. got a U certificate (our lowest rating, equivalent to a G) and Poltergeist got an X (our highest rating, akin to an R). Between U and X were two other ratings, A, and AA. I don't think such a drastic disparity between US and UK ratings has ever occured before.

I talk about it more here, if you're interested. :)

https://medium.com/fan-fare/poltergeist-40-years-on-b81e0a5dd53f