When you say you believe this, do you mean you believe it to be the case, or you believe it to be a realistic possibility?

Well naturally I believe the latter, but I also believe the former in the sense of being more likely true than not.

I stumbled across Tipler when reading up on the simulation argument, and it inspired further “am I being a crackpot” self-doubt, but I don’t think this argument looks much like his.

Tipler isn't a full crackpot. His earlier book with Barrow - the Anthropic Cosmological Principle - was important in a number of respects and influenced later thinkers such as Kurzweil and Bostrom.

Tipler committed to his particular physical cosmology which is now out of date in light of new observations. Cosmological artificial selection (evolution of physics over deep time via creation of new 'baby' universes by superintelligences) is far more likely. In any kind of multiverse, universes which reproduce will dominate in terms of observer measures.

considerations with “watering down” simulations through AI “thought crimes,” that can be considered once this is brought in.

Not sure what you mean by this.

The idea of posting about something that is unpopular on such an open-minded site is one of the things that makes me scared to post online.

Don't let that stop you. You can post it on your blog then discuss it here and elsewhere. LW discussion is more open minded these days.

I am also atheist, and grew up very religiously Christian, so I think I also have a strong suspicion and aversion to its approach.

I was an atheist until I heard the sim argument and I then updated immediately.

It is interesting to look at the various world religions in light of Simulism and the Singularity. Some of the beliefs end up being inadvertently correct or even prescient.

For example, consider beliefs concerning burial vs cremation. It's roughly 50/50 split across cultures/religions over time. Both are effective from a health/sanitation point of view, but burial is somewhat more expensive. Judeo-christian religions all strongly believe in burial (cremation was actually outlawed in medieval europe). Hinduism on the other hand strongly supports cremation.

In the standard (pre-singularity) atheist worldview, these are are just arbitrary rituals.

However, we now know that this couldn't be farther from the truth. Burial preserves DNA for thousands, if not tens of thousands of years. So at some point in the near future robots can extract all of that DNA and use it to help in resurrection simulations. Obviously having someone's DNA is just the beginning of the information that you need for mind reconstruction, but it's a very important first step.

There are number of other features/beliefs like this that western religions (and xtianity strains in particular) probably got right. The general idea of a future hard eschatology (end of human history - rapture/singularity), resurrection of the dead, afterlife reward judgement by future super-intelligence, divinization/deification) (humans becoming gods) ...