Basically, Northern Ireland has a cultural legacy that nowhere in the UK shares and one that is very different to the Republic of Ireland and that is its Sectarian history. What people have to understand about NI is that while the population is roughly divided in half between Catholics and Protestants, Protestants tend to be more hard line in Northern Ireland than in the rest of the UK, subscribing to conservative Presbyterianism of the fundamentalist Bible bashing kind. Don't forget that a sizable section, 40%, of people questioned at the DUP (NI's largest and governing party) party conference in November last believe that creationism should be taught in schools, thats higher than most Bible belt states in the USA. Further to this, the political situation and the cultural history of NI Protestantism has given that section of society a siege mentality that is distinctly conservative and obstinate.
For the Catholic population, Northern Ireland's history has endowed them with a conservatism that isnt found as much among their co-religionists in the south. Society is very rural in Ireland and as a result, things do tend to be a bit backward but unlike the Republic, Urban centres tend to be more protestant while rural areas tend to be more Catholic. The protestant effect gives NI's towns and cities (except Belfast which is quite progressive) a more conservative air and the rural areas that look to these urban areas are naturally endowed with the values and tastes of the urban population. On top of that, Catholicism's traditional stance on homosexuality has certainly left its mark on the Catholic population but I will argue that the Catholic section of NI society is more open and friendlier to LGBT issues than the Protestant section, although I am fully open for correction on that. Sorry, this turned more into an essay than a reply.