Living with them is not the problem. The problem is when they start blowing their bombs off left and right, or giving them to terrorists or other rogue nations to do so.
Yes, given human nature, and history-
eventually some podunk nation is going to try to play the nuclear wild card, in a gamble to show up a major nation.
How we handle Iran sets a template in play.
We need to establish the template as
"don't play nuclear".
We need to demonstrate that proliferation by rogue states is an immediate no-win, non-starter.
KABOOM, you lose.
No discussion, no UN.
Kaboom, you lose, podunk nation.