We don't have to do this, but if we do, then any trouble in Ireland will solely be the fault of the Irish.
It will not be any 'we' who is putting peace at risk.
Let me just check that:
When you say "the Irish," do you include citizens and residents of the United Kingdom?
Was it the Irish who decided to break up the free-trade arrangement that has made cross-border smuggling so much less profitable? And weakened criminal gangs by hitting them in the pocket?
Disregarding "fault," where will the young soldiers come from who will in future lay down their lives in a futile attempt to negate hundreds of years of hatred and violence?
And where will the taxpayers come from who take on the monetary cost?