Although religion might be the obvious target of Wells' satire, it's not necessarily the only target. The Law is broad enough in how the Beast Folk use it that it could be a satire of any set of rules in society.
The Law hides from the Beast Folk the fact that they are animals. So long as they have the Law, they believe they are men. But according to Prendick, the Law conflicts "in [the Beast Folk] with the deep-seated, ever rebellious cravings of their animal natures" (15.5).
Human society's rules work the same way. They shield us from the fact that we are animals by allowing us to pretend that, because we are a rule-governed civilization, we are something totally different. We can sit back and relax in our belief that anyone who follows the rules is better than an animal, while anyone who breaks the rules, well, they don't deserve to be taken as fully human and should be punished.
Of course, the conflict between beast and human that Prendick mentions happens inside all of us. We just don't always like acknowledging it. Prendick says that the Beast Folk
"were really hypnotised; had been told that certain things were impossible, and that certain things were not to be done, and these prohibitions were woven into the texture of their minds beyond any possibility of disobedience or dispute." (15.5)
Sound at all familiar? Can you think of examples where we humans ever behave like we're "hypnotized"? Where it doesn't even occur to us that disobedience or dispute might be an option?
For a rule to work, it needs to have a punishment attached to it. Otherwise, why bother following the rule? When we're young, our mom will give us a time-out or not let us watch TV for a while when—totally hypothetical example—we've taken a pair of scissors to her expensive cashmere scarf. As we get older, society takes over where our parents leave off. Being grounded for staying out too late is replaced with fines for parking in front of a fire hydrant and prison time for robbing a bank—which is kind of like being grounded for a long, long time.
The House of Pain is social punishment for the Beast Folk. If the Law is seen as religious, then the House of Pain is basically their Hell. Like any good hell, the details are disturbing but minimal. When Prendick first enters the place, he describes it like this:
"There was blood, I saw, in the sink, brown, and some scarlet, and I smelt the peculiar smell of carbolic acid. Then through an open doorway beyond in the dim light of the shadow, I saw something bound painfully upon a framework, scarred, red, and bandaged. And then blotting this out appeared the face of old Moreau, white and terrible." (10.21)
Wow, sounds pretty much like Hell to us (or the set of one of the Saw movies). Beyond that, all we know is that any Beast Folk entering the place is vivisected, without pain killers, until they are deemed more human.
In the larger scheme of things, the House of Pain represents punishment for breaking social rules in general. But think about it: On one hand, it's our rules that give us the sense that we're more civilized than animals—who don't have any rules. On the other hand, if these rules would come to us naturally, would we need punishment to enforce them? Heck, would we even need the rules in the first place? In fact, maybe the reason fear of punishment works so well to keep us in line with the rules is because being afraid of pain is very much an animal instinct. As Moreau says, it is the "mark of the beast" (14.26) in us.
Of course, this view of punishment totally ignores ideas like empathy and altruism. What do you think? How does something like empathy or goodwill fit in with an idea like the House of Pain?