Except for a few isolated incidents and terrorist acts related to N. Ireland, there has been no religious-based Christian terrorism for hundreds of years. Contrast that with daily, ongoing Muslim terrorism and decide which is the religion of peace.
Northern Ireland is even a little more complicated than that. English (protestants) versus Irish (Catholics).
The religious aspect is secondary to the nationalistic aspect.
And even those Irish Catholic/Protestant clashes were mostly about politics, not religion.