I’m very confused how this could possibly be conflated with the 5 heavy acts. The sutta in question says,
unless he abandons that assertion and that state of mind and relinquishes that view, then as surely as if he had been carried off and put there he will wind up in hell. Just as a bhikkhu possessed of virtue, concentration, and wisdom would here and now enjoy final knowledge, so it will happen in this case, I say, that unless he abandons that assertion and that state of mind and relinquishes that view, then as surely as if he had been carried off and put there he will wind up in hell.
Which is fundamentally different than the 5 heavy acts, in that it’s explicitly reversible. Ajjasattu couldn’t unkill his father to achieve stream-entry, Devadatta couldn’t un-draw the buddha’s blood, etc. I think this is enough to say that what the buddha is describing here is different from the sort of immediate condemnation of the 5 heavy acts.
Once we accept that distinction, I think it makes sense that obviously someone who denies the truth of Buddhism necessarily will not follow the noble eightfold path, thus will not attain stream-entry, thus will achieve lower rebirth. I think this interpretation is strengthened by the contrast made to one who practices earnestly achieving nibbana.
Of course, there’s a sort of hyper-literal reading where you’d imagine 1st year philosophy students whisked away through a portal to hell the moment they write a paper saying, “Siddharta Gautama logically deduced…” but that same sort of hyper-literal reading would tell you that every monk on this forum is an arhant because they “are possessed of virtue, concentration, and wisdom”. Clearly, neither is what is meant by this passage.
I don’t think that’s true. Five precepts lead to good rebirth and don’t lead to bad rebirth, but they don’t guarantee you won’t be reborn in a lower realm (due to other / prior actions).
You may be thinking of this sutta, but I believe that’s specifically about 5-precept lay followers who are also stream-winners.