> I grappled with the decision to have brises for my sons. I don't think it's possible to know or define how traumatic such a procedure is; is it worse than giving a 6-month old pierced ears?
Yes, the foreskin doesn't grow back
> Is it worse than travelling through the birth canal and having your umbilical cord severed?
Yes, because travelling through the birth canal is required to live, and doesn't affect sex in later life. Also, it doesn't result in any amputations.
> Who knows. As obvious as it may seem, the pain of a bris impossible to gauge.
We do. There's a ton of nerve endings there. Slicing of a particularly sensitive area (due to the concentration of nerve endings there) is going to be painful. If you want to do it, you need to show some evidence that it is not, not throw your hands in the air and say "well, we don't know").
> There's a lot of discomfort, maybe pain, but as a father of 3, I assure you every doctor's visit and many trips to the park involve similar levels of harm.
I think your are deluding yourself - few doctors visits or trips to the park results in cutting off a very sensitive part of the body.
> It's not an easy topic,
It is a fairly easy topic. The question of "Should we amputate a part of a newborns body, one that affects future enjoyment, and known to be incredibly sensitive" is an easy one to answer.
It becomes complex when the addition of "But my beliefs, unsupported by any evidence, mind, require me to perform this operation."
The long and short of it is, it doesn't matter how much evidence there is showing that the pain is real, and severe, and the lifelong effects are real; you've done it based on a belief that supercedes mortal pain and suffering.
In other words, it doesn't matter what the facts are, because the conclusions by the proponents have already been made[1].
[1] Imagine, for a moment, that we are in the near future where we have a device that lets us quantitatively determine (on a scale of 1-10) how much pain is being experienced, with 1 = barely perceptible and 10 = just below the point of passing out, with 5 = minor surgery without anesthetic.
What number would religious proponents need to see before they say "that's too much"? Five? Seven? Three?