Since when has something being immoral stopped anybody from doing it?
I agree with the sentiment of this and certainly the proposal that for some beings simulated universe to the level we experience might be technologically possible does not proceed from any moral argument.
Any absolute morality would be that of the simulator.
As would the purpose of the whole simulation.
Tegmark has said that the underlying purpose of a simulated universe would be interest. Dullness he says might risk deletion so Tegmark suggests we should all be doing interesting things.
That means every regular on religion ethics is doomed.