Why does England not have sectarianism like Scotland and Northern Ireland?

Here is Ed West's answer:

The most likely answer is demographics. Irish immigration to Scotland was, proportionately, much larger than in England, with Irish Catholics accounting for 12-15 per cent of the population, and much higher in the West of Scotland. In England the Irish population peaked at around 3.5 per cent of the population in the 1860s and 1870s, when Holborn and King’s Cross were Irish slums. And even though the Irish genetic component of the English population probably doubled over the next century before the Tiger economy shut off immigration, the earlier populations had by that stage lost their ethnic-religious identity and married into the native population. Liverpool, the most Catholic city in England, was possibly 25 per cent Irish or second-generation Irish at one point, Manchester less than half that, and Birmingham and London even smaller proportionately.

The Irish Catholic population was simply not big enough to make sectarianism the lasting issue in England that it is in Scotland, or Northern Ireland, where a Catholic population of 35 per cent was enough to lead to conflict.

And if two white ethnic groups can't live together peacefully then what hope does a multiracial society have?