You asked about consensus. The correct answer to that question is that there isn't consensus. There isn't even consensus as to whether humans can wind up in "hell" in the first place! (See "universalism".)
That said, I and many Christians consider universalism heretical; there is much evidence both from scripture and from observing real people that not everyone wants to spend an eternity with God, and I believe God does not force Himself on anyone. Rather, I believe that all those who desire God will find Him, and that He doesn't force Himself on those that don't.
As to what happens to those that don't desire God, opinions vary. Some believe in annihilationism; that is, those who aren't saved will (eventually) cease to exist. Others believe in perpetual torment. One rationale given is that humans are so consumed by sin that we fail to appreciate its severity. (Passages such as Matthew 5:29-30 are sometimes used to support this.)
What's important to note here is that many believe that punishment for sin is not a "one size fits all" matter. Again, scripture supports this, e.g. Matthew 10:15. If one imagines "hell" as a spectrum of possible outcomes, some of which may involve either some sort of cessation of existence, or at least a lessening into ennui (e.g. Lewis's The Great Divorce), the idea that perpetual torment is reserved for the likes of Hitler is far less offensive.
Then again, your premise of infinite punishment for finite sin may be flawed. We know that those redeemed will be truly free from sin, but it's unclear if all will be free from sin after Judgment.
Thus, to summarize, there are several possible responses to your objections:
- The severity of sin is not understood / greatly underrated.
- Sinners continue to sin in eternity; therefore, infinite punishment is not for finite actions.
- Infinite punishment doesn't apply to all humans, and possibly to none.
It's also possible that all of the above are true.
I would also strongly recommend this video by Mike Winger, which directly addresses some of the points raised in the Question.